Charities that claim to have no fundraising costs should be "called out and held accountable", according to a report co-written by the fundraising consultant and academic Adrian Sargeant.
The report, Growing Philanthropy in the United States, published last week, summarises 32 recommendations for increasing donations.
The recommendations were made by 35 US philanthropy experts at a summit convened in August by the fundraising software company Blackbaud, Indiana University and the fundraising consultancy Hartsook Companies.
One of its recommendations is to "blow the whistle on organisations claiming to have zero costs of fundraising".
The report says: "Although donors are interested in the ratio of administration costs or fundraising costs to total expenditure, there is evidence that many non-profits simply exaggerate this performance in the absence of a well-regulated reporting regime, thereby misleading the public.
"The summit was emphatic that no non-profit reporting public donations should claim to have zero costs of fundraising.
"If they do so, they should be called out and held accountable for the damage that they do to the public trust."
Although the report says that progress has been made in this area in the UK, Jen Shang, a co-author, told Third Sector that it was still an issue.
"There’s no such thing as zero cost of fundraising," she said. "There needs to be better education of fundraisers, board members, executives, the media and the public so that they understand this.
"People need to know that the cost of fundraising is not a bad thing. Whatever they’re spending, it’s good expenditure. Somehow that message doesn’t get mentioned as often."