ARB rebel Ian Salisbury has predicted that the board will soon be forced to abandon the Part 3 qualification.
The RIBA presidential candidate has revealed details of legal advice that warns the board's bosses that, if the Part 3 requirement is challenged in the courts, it will have to be abandoned.
The advice says that, because foreign-qualified architects that come to the UK are unrequired to take Part 3, there is no legal reason why British-trained architects should be forced to take the qualification.
In a written statement, Salisbury said he believed the change was inevitable, especially since the proportion of foreign architects using this loophole has increased to 20 per cent of the total registering each year.
'I have seen a copy of that advice, ' he wrote, 'and it seems to me to be quite wrong for the ARB to be insisting that UK candidates present Part 3 qualifications given the advice the board has received.'
But the Oxford-based practitioner added that he believes the potential change would benefit the RIBA.
'I see every advantage in drawing a distinction between the stature of a mere registered architect and the gold standard of being a chartered architect, ' he said.
'Moreover, the distinction will do the institute a great deal of good as soon as the public begin to appreciate that there is a substantial difference between the two.
'It will also maintain the attraction of the institute to overseas members unable to obtain a similarly high professional standing in their own countries, ' Salisbury added.
However, the ARB's chief executive Robin Vaughan insisted that there was a little chance of change.
'We last looked at this back in 2000 and we agreed with the RIBA that the current setup is completely acceptable and we see no reason why this should have changed, ' he said.
'I also find it interesting that many of the foreign architects that come to this country choose to do Part 3 even though they do not have to, because they think it is such a good thing, ' he added.