In March, a report from think-tank NFPSynergy found that 43 per cent of those polled said they were irritated at being called at home by charities.
PDSA's Cubitt is not surprised, although he believes the main culprits are calls from commercial organisations: "I hate being rung up by my bank trying to sell me insurance when I'm sitting down to dinner."
He adds that, as more and more people become irritated by telemarketing generally, the whole sector could find itself facing further regulation.
Currently, there is a 'do not call' register, called the Telephone Preference Service, which means that around 20 per cent of people on any list submitted to agencies by charities cannot be contacted.
But some believe that rather than opting into the service, there could be pressure to make it an 'opt-out' service. In other words, charities could only telephone individuals who have specifically agreed to be contacted.
NCH's McKay believes there will probably be more restrictions in the future: "If you look at what's happening with tighter regulations on email marketing, we'll probably see a similar trend with the telephone as well."
Pure's Eserin also believes it is mainly commercial telemarketers to blame for irritating the public, rather than charity fundraisers. Although there are already guidelines on telephone fundraising from the Institute of Fundraising, he says there are moves afoot to establish a forum for telephone fundraising agencies, which would discuss issues of relevance to the sector and promote good practice.
Kathy Howard, head of telephone fundraising at the RNIB, says: "We're making 20,000 calls a night and the number of complaints is very low. I'm an old-fashioned fundraiser and I believe that the passion and commitment of our callers is accepted well by the public."
But she acknowledges that, as more people become aware of the Telephone Preference Service and register not to be called at home, the RNIB's telephone fundraising operation will become more difficult. "We continue to look at the market because our fixed costs are rising, due to more people signing up to the service."
CASE STUDY: THE RNIB
The RNIB uses both an outside agency for its telemarketing and a network of home-based callers
The charity's home-based callers make make up a "virtual call centre".
There are 34 teams of home-based callers, mainly working in the evenings, and they make 20,000 calls a night asking people to sell RNIB raffle tickets or put collection boxes in their homes.
"The home-based operation has become bigger and bigger over the past 10 years and now brings in £8.4m a year," says head of telephone fundraising Kath Howard.
The charity used the agency Pell and Bales to try to upgrade those supporters who responded to direct mail appeals to become committed givers.
Howard distinguishes between the specialist skills offered by Pell and Bales and the "high-volume, low-value" operation run in-house.
"We keep the raffle calls in-house because it's the sort of operation where you have to make a large number of calls to bring in a relatively small revenue," says Howard. "It probably wouldn't be cost effective to use an agency for that kind of work."
There is, however, some overlap between the work of the agency and that of the home-based workers.
"We've recently been testing new approaches by our home-based workers to turn raffle sellers into committed givers, and that's been very successful," explains Howard.
Who is best placed to make vital fundraising calls or to develop relationships with donors - you or an outside agency? Patrick McCurry examines the pros and cons
Telephone fundraising's popularity has come to the fore in the past 10 or 15 years, and it is now a valuable source of income for many charities.
It is a sector dominated by specialist agencies, but, encouraged by the revenues, some charities have chosen to set up their own in-house call centre operations. But what kinds of telemarketing can best be done in house and which operations are usually best contracted out?
Of course, much will depend on the size of the charity, because significant resources will be needed if a charity decides to run its own telemarketing.
The advantages the move offers charities is the direct control over the operation, and the knowledge that it is not putting its reputation into the hands of third parties.
The disadvantages are that the charity will have to develop in-house expertise in telephone fundraising, train staff and bear all the overhead costs.
Kathy McKay, relationship marketing manager at NCH, says that her charity outsources all of its telemarketing. "We don't have the volume of telephone fundraising that would justify us doing it in-house," she says.
Instead, NCH uses agencies for specific campaigns. "We don't have a big enough database of names to support continual campaigning, or to employ full-time staff on telephone fundraising."
She stresses that telephone fundraising is often a specialist activity and that for NCH to do it in-house would involve a major recruitment and training programme, along with ongoing supervision and management of callers.
"It's a specialist skill set and most charities don't necessarily have those skills in-house - it's not that easy to know how to make the 'ask'," she says.
But McKay acknowledges that there are disadvantages in outsourcing telephone fundraising - as with any form of outsourcing. One drawback is that most agencies charge per contact. "Some agencies charge on a results basis, but it's not an industry standard," she says.
She adds that a further drawback is that third-party contractors will never be as knowledgeable about the charity as in-house staff.
But animal welfare charity PDSA has split its telemarketing between an in-house call centre in Sunderland, and two external agencies. The Sunderland centre was established in 1996 and has 36 operators calling individuals who have already had some contact with the charity, and asking them to collect money from households in their area.
For other work, such as cold-calling and persuading individuals to become committed givers to PDSA, the charity uses external agencies because of their expertise in sales.
"We're looking for more specialist skills in this area, and a harder sales edge," says Paul Cubitt, group product manager, committed giving.
"The agencies we use are well established and know the ropes. They have quality operators who offer us added value because they're very good at dealing with people on the phone and have refined their approach over time to avoid any potential backlash about over-aggressive calling."
For those charities that are tempted to outsource their call centre operations, it is important to ensure that they will get value for money, and that they are dealing with an agency that they feel comfortable with.
PDSA's approach of using two agencies to run its telemarketing is one way of reducing the risk of paying over the odds.
Rob Reaks, chief executive of agency PTF, one of PDSA's agencies, says: "Splitting your contract between two agencies is a good way of keeping the agencies on their toes because it gives the charity a way of comparing performance."
He also argues that charities should periodically test whether they are getting a good service from their existing supplier, by testing its performance against other agencies.
"A lot of direct-marketing managers in charities say they'd like to carry out tests, but are simply too busy. In reality, it doesn't take that much effort to see how another agency would handle the business," he says.
John Eserin, marketing director at agency Pure, says there are differences between agencies, and that it is important that a charity finds one that reflects the charity's own values in treating people.
Eserin adds that, increasingly, charities are using their telephone fundraising not as a standalone tool, but as part of an integrated fundraising strategy that includes face-to-face, direct mail and other approaches.
He says: "Instead of having a list of people whom you phone up once a year, more charities are seeing the value of integrating their fundraising. It's becoming more feasible because agencies have become more sophisticated in the ways that they can target and segment particular audiences."
There are around eight or nine well established agencies offering telephone fundraising, says Reaks: "There are some new kids on the block, which may well be ambitious and have good intentions, but charities should always do their own research to find out if a particular agency can live up to its claims."
Consequently, says Reaks, charities should not be too taken in by testimonials, but should instead visit the call centre operations of any agency that they are considering using. "It's essential to visit the call centre and observe the callers in action. How do they treat the people they contact? Are they building a relationship with those people or just trying to screw money out of them?"
On the issue of fee structures, Reaks says that PTF would charge on a results basis for cold calling but where it is calling individuals who already have some connection with the charity, it charges on a 'per-contact' basis in order to avoid over-aggressive selling.
An agency that is too focused on persuading individuals to donate may offer good short-term results, but in the long-term this could turn out to be counter- productive because direct debits may be cancelled subsequent to sign-up, and people may complain about a charity's 'aggressive' approach.
"You can often persuade people to donate because, even if they don't really want to, they don't want to say 'no' to charity," says Reaks.
PDSA's Paul Cubitt argues that protecting the reputation of the charity is of paramount importance when deciding to outsource telemarketing. "That's why we do a great deal of work on ensuring that the information we give the agencies is accurate, that the operators receive good training and that we take complaints extremely seriously.
"Fortunately, complaints are relatively rare and we sometimes adopt a 'mystery-shopper' approach, in which we include the numbers of PDSA people in the lists we give agencies. That enables us to witness at first hand how they handle calls."
But there are sometimes areas of tension connected to outsourcing telephone fundraising.
Jeff Williams, national secretary for Christian Aid in Wales, acknowledges that he is "ambivalent" about it's use as a fundraising tool. "Sometimes telephone fundraising that is organised centrally, and usually outsourced, can come into conflict with a charity's community fundraising," he says.
Christian Aid's fundraising is very much community-based, he says, and it can cause tension if telephone fundraisers are ringing up people in a particular locality at the same time as there is community fundraising activity going on.
"Sometimes even the community fundraisers will find themselves contacted by telephone fundraisers for the same charity," says Williams.
Last year, he tried to recruit some volunteer community fundraisers to set up a telephone fundraising team, but found little interest. "I think they were worried they didn't have the skills, and they were also a bit sceptical about the whole process," says Williams.
This difficulty perhaps partly explains why so many charities outsource their telemarketing operations.
Another issue that charities are having to grapple with, whether they carry out telephone fundraising themselves or outsource it, is the possibility of increased regulation of the telephone fundraising sector. Although any charity or agency involved in telemarketing will say it deals sensitively with the people it calls, it seems that much of the public remains to be convinced.