Will Alsop has condemned the lack of quality candidates for the RIBA presidency and called for members to quit the institute and support the Architecture Foundation instead.
Alsop criticised the limited outlook of presidential hopefuls George Ferguson and David Thorp.
And he remained steadfast in his decision to abstain from voting in the forthcoming elections despite the news that a third candidate, Annette Fisher, had joined the race.
Dismissing the RIBA as irrelevant, Alsop said he would be resigning - and urged others to do the same. 'What is the relevance of the RIBA to me and other architects?' he asked. 'What are its achievements during the past ten years? Why spend money on it?' As a non-RIBA member Alsop would not be eligible for RIBA awards including the Stirling Prize.
Alsop's criticisms come as Fisher, RIBA vice president for communications, confirmed her commitment to stand following speculation that she was in the running. Fisher said she had received overwhelming offers of support, including one from ex-president Marco Goldschmied.
Fisher joins Bristol-based George Ferguson and anti-London candidate David Thorp. Ferguson has criticised the attention given to 'the small band of star architects' and identified a need to defend regional practice from 'fashion slavery', while Thorp has pledged to speak for the small practitioner.
Describing Thorp and Ferguson Alsop said: 'One of them is against London and the centralisation it represents (talent tends to gravitate towards the capital), and another is set against the 'star' system of architecture, whatever that is. As I live and work in London, and happen to be relatively well known, I have no choice but to not vote.'
And he added that it was time London fought back. 'It's a wonderful place full of wonderful architects.' The RIBA should get on with being a trade union, he argued, and leave the promotion of architecture to the Architecture Foundation.
Meanwhile, newcomer Fisher denied suggestions that she would be running a 'diversity' campaign to become the RIBA's first black female president. 'I can't win on the basis of race and gender alone, ' she said. 'I get the feeling there is support out there for me. If I win it will be because the majority want me there and believe that I can make a difference, add value and have something extra to bring.' She added: 'I'm beginning to think that perhaps the RIBA is ready to elect me. Just my being in the race is a big change. I think people will sit up and take notice.'
Former president Goldschmied applauded Fisher's decision to stand. 'She would make a great change from the usual faces of white males in their 50s and 60s from large practices, ' he said. And he urged the younger generation to exercise their right to vote. 'You can't change the institute by abstaining, ' he said.
Front-runner Ferguson was not fazed by Fisher's decision, but said it would add interest to the campaign. He said he had received confirmations of support from the many 'eminent' figures backing him, including David Rock, Eva Jiricna, Bob Allies and Rod Hackney. Ex-director general Alex Reid - who has ruled himself out of the running this time around - is also backing Ferguson.
Small practice candidate David Thorp said he remained confident that he was in with a chance, and he pledged to promote the views of those 'whose business is small works, not medal-winning showpieces'.
The deadline for nominations is today, Thursday 28 February.Voting will begin in April, with the successful candidate serving as president in waiting before taking up office in summer 2003.