Boswell has condemned as "unhelpful and irresponsible" charities that promote in their marketing the fact that they spend nothing on raising money. He claimed this undermines the efforts of other charities to be open about their fundraising costs.
He said: "Any fundraising organisation that promotes itself at the expense of other charities and the reputation of the sector as a whole is acting highly irresponsibly."
Comic Relief states that on Red Nose Day, all of each donated pound goes to its chosen projects. Lions Clubs International published research in March that suggested that nearly a third of people in the UK would rather donate to charities that spend the whole of their contribution on the cause.
Boswell added: "Comic Relief is, understandably, presenting a rosy picture for itself. But in doing so, it is polarising the view that fundraising has no cost."
A spokeswoman for Comic Relief said the charity can keep the promise because its running costs are met in cash or in kind from other organisations, including the Government, corporate donors and individual suppliers, as well as through investment income and interest generated on the charity's funds.
She added: "Trustees believe that this promise provides an important reassurance to the public.
"It does not imply that Comic Relief doesn't incur costs to achieve its fundraising, nor that such costs are not necessary for charities to raise money from the public."
Boswell is part of the sector-wide group, led by Shelter fundraising director Alan Gosschalk, that is encouraging charities to be more open about their fundraising costs to improve public confidence in the sector.
He said charities' boast that every penny in the pound goes to the cause does not take into consideration any previous investment for the infrastructure of the organisation, or money from sponsorship.
He added: "It is the responsibility of the charities to explain why they are spending money on fundraising."
Alan James, spokesman for the Lions Clubs, which has an army of volunteers, said: "We are proud of what we do. It is not our problem if other charities see that as unfair."
- Institute of Fundraising chief Lindsay Boswell has criticised charities that pledge to spend every penny of received donations on the cause
- One such charity, Comic Relief, has defended its position, saying that the pledge provides important reassurance for the public
- The Lions Club dismisses criticisms as "not its problem".