The boycott campaign was launched last week by consultancy Company Solutions after Third Sector stories that the Royal Mail's mechanised Freepost sorting system was unable to recognise stamped envelopes and was generating an automatic charge to charities (Third Sector, 11 June).
"Our members tell us that the inclusion of a Freepost envelope is an effective tool that helps ensure the best return on investment is achieved for charity fundraising appeals," said Megan Pacey, director of policy and campaigns at the institute.
"I therefore do not believe that boycotting the Freepost service is in the interests of charity fundraising appeals or moves the situation forward."
She declined to advise charities on a general solution or the question of whether they should continue to ask donors to save them money by putting stamps on Freepost envelopes.
"The Institute of Fundraising is working with its members to support them in identifying solutions that meet the needs of their organisations," she said.