The launch is now scheduled for spring 2007. In a statement, the FSB said that it would not be revealing the exact date until mid-December.
Jon Scourse, director of the FSB, had previously told Third Sector that the scheme would open for business in January next year.
The launch was originally planned for 10 October (Third Sector, 6 September), but was postponed because fewer than 100 charities had signed up.
The board was expecting a surge in membership after the publication on 10 October of the Fundraising Promise - six promises from charities to donors that form the basis of the scheme.
The FSB declined to reveal the number of fundraising organisations signed up, but a spokeswoman said: "The board has been very encouraged by the considerable increase in the level of enquiries and applications coming in since the launch of the Fundraising Promise."
None of the top 10 fundraising charities have so far joined the scheme, according to a Third Sector survey, but they have all signed the board's 'statement of intent' or said they planned to join.
Peter Cardy, chief executive of Macmillan Cancer Support, said there was no lack of will among large charities, but many were likely to be waiting for agreement from their trustees. "The FSB has to take its place in the order of business," he said.
Scourse is now focusing on a drive to recruit Scottish charities and is also scheduled to meet staff from Save the Children this week in an effort to persuade the charity to join.