Speaking in a seminar at the Institute of Fundraising's annual conference last week, senior staff at Barnardo's, the Multiple Sclerosis Society, the NSPCC and the RNIB said that shock adverts are sometimes unavoidable and are often very successful.
But they also warned that charities have to get the balance right to avoid upsetting supporters and beneficiaries. "Setting out to shock for the sake of it is wrong - but using shock to get an important message across can be right," said John Grounds, director of communications at the NSPCC.
The sector has recently come under fire from commentators and the national press for using shock tactics gratuitously.
An advert by the British Heart Foundation depicted a woman with a plastic bag over her head with the strapline: "I've got heart failure. And this is what it feels like every morning". It won the dubious accolade of being last year's most complained about advert (Third Sector, 7 May).
WWF was also forced to relaunch its campaign against toxic waste after the Advertising Standards Authority ruled that the charity's original advert showing an unborn child in the womb was "unduly alarming" (Third Sector, 14 May).
Barnardo's and the NSPCC are renowned for their own shock adverts, and the Multiple Sclerosis Society has also run a series of stark images showing the effects of the disease.
Grounds argued that for some charities shock tactics are part of the territory because their remits are intrinsically shocking.
He added that people often forget that public education and campaigning are part of the NSPCC's charitable remit. As a consequence the charity is obliged to tell the public about the harrowing situations that it deals with.
The four charities also claim that hard-hitting messages are needed to cut through the raft of information that the public is exposed to each day.
"In 2002, a total of £8.1 billion was spent on advertising and only £54.8 million of that was charity advertising, which is just 0.6 per cent," said Lynne Stockbridge, head of communications at the RNIB. "Charities simply can't compete, so many use shock tactics to get their message noticed."
There is no doubt that shocking adverts can be very effective. Barnardo's used dramatic images of children in adult situations, including a picture of a baby injecting heroin, as part of its drive to catapult its brand into the modern era. As a result, the public's spontaneous awareness of Barnardo's has increased from 28 per cent to 44 per cent.
"The campaign was successful because the debates that ensued were about the issue and not about the adverts themselves," said Diana Green, head of advertising and communications at Barnardo's.
However, the charities stressed the importance of balancing the shock content of adverts. Barnardo's now works with the ASA before releasing its campaigns to make sure that they don't breach any rules.
The Multiple Sclerosis Society found that its portrayal of the disease during a campaign in the 1990s succeeded in increasing public awareness, but created a backlash from its beneficiaries.