The Office of Fair Trading has forced the RIBA to shelve its Recommended Fees Guidance, a move that observers have warned will slash incomes for small practices.
The OFT has instead ordered the institute to publish details of its 2002 market research, which show architectural rates as much as 40 per cent lower than in the last fees guide.
Practitioners fear that clients will use these new statistics as a weapon to negotiate architectural rates down to a new low.
Hourly fees represented in the market research - to be published in the new Clients' Guide within weeks - are up to £30 lower than in the guidance, while the recommended construction percentage for small projects has fallen from 18 per cent to 12 per cent.
The OFT has been investigating the RIBA's Code of Practice throughout 2003 and in July it forced the institute to drop the pivotal Clause 3.3, which prevented architects from undercutting one another.
But RIBA councillor Chris Roche said he was most dismayed by this latest development. 'The institute has simply given in to pressure when it should be fighting our corner, ' he said.
'We are supposed to send these figures to our clients - a move that would be completely detrimental to business. The OFT should understand that if they drive down fees then architectural standards throughout this country will be lowered.
'The RIBA should have stood up to the government instead of simply rolling over and giving in, ' Roche added. 'This is a disgrace.'
And small practitioner George Pace of Dunthorne Parker Architects said he was amazed by the news: 'I think it is pretty likely most major clients will take into account this downward trend and use it when they are negotiating. We lost the mandatory fee scale under Thatcher and it is devastating to discover that this supposedly centre-left government has made the situation even worse. I feel really embattled over fees at the moment.'
However, the RIBA's new practice director Richard Brindley insisted there was nothing to worry about. 'This is only market research and I believe clients will understand that.
'These market research figures are not a guidance and I do not think they will be treated as such, ' he said. 'They simply show how much architects have actually been paid.'
The OFT and the Department of Trade and Industry were unavailable for comment.