They did so following revelations that the firm was charging clients fixed fees to meet them.
The Lord Chancellor Lord Falconer and Stephen Timms, chief secretary to the Treasury, withdrew from the events, alongside sports minister Richard Caborn and Kevin Barron MP.
The Times published the revelations on its front page last Saturday, having obtained a leaked email from BPPA inviting clients to sign up to the events. It is thought the fee attached would be in the region of £5,000.
As delegates reflected on the speeches of Gordon Brown and Tony Blair, and wife Cherie's alleged ‘lie' gaffe, it was the BPPA story that set lobbyists' tongues wagging across the conference venues in Manchester.
Explaining the ministers' withdrawal, BPPA managing director Peter Bingle admitted to PRWeek: ‘They didn't want to be linked to the idea of cash for access.' He added that the fees were necessary to ‘offset' the various conference costs of entertaining clients.
Timms was replaced by William Hague's former press secretary Amanda Platell, and Andrew Pierce - ironically, of The Times - who is to become assistant editor at The Daily Telegraph.
It has also emerged that one of the politicians named in the email - health minister Caroline Flint - never agreed to attend a BPPA function.
The revelation is the latest ‘lobbying scandal' to damage the image of the PA industry. Although one of PA firms' main functions is to provide clients access to politicians, as well as expertise, it is a service that is provided conventionally as part of a wider contract.
Weber Shandwick director of corporate and PA Michael Prescott said: ‘It is pretty rare to come across firms packaging up lunches, drinks and receptions in a kind of "cash-for-access" way. Public perception of this industry is important.'
Others said BPPA's approach was not unique but that the agency had been ‘stupid' to send such an email. One in-house lobbyist said the email was ‘a plague on all the public affairs consultancies' houses'.
He added that it served as a ‘hurry-up call for trade bodies' such as the Association of Professional Political Consultants (APPC) to forge ‘co-operation on openness' in lobbying across in-house and consultancies. BPPA is not a member of the APPC.
On the potential fallout for the industry, PRCA public affairs committee chairman Rod Cartwright said: ‘It's a shame that people don't think about the industry as a whole but only about themselves.'