The infamous anti-ARB campaigner said that he would stand down to concentrate on campaigning against the quango 'from the outside'.
The Oxford practitioner claimed he had left because he felt unable to represent the interests of those who voted for him.
Speaking last week, the former RIBA presidential candidate attacked the board, furiously claiming the entire body should be wound up through the repeal of the Architects Act.
'There are many reasons why I am leaving but mainly I feel desperately uncomfortable being part of this dysfunctional organisation,' he said. 'My views have changed and I now believe that the act must be killed off. This is a long way from my election statement and therefore I felt I must resign.'
But Salisbury said that he would not give up the battle just because he will no longer attend board meetings. 'This matter is not over for me as I am under investigation for my compliance with the PII cover,' he said.
'I also intend to remain involved with the campaign because the ARB is doing a disservice to the public by harassing the profession,' Salisbury added.
Paul Hyett, RIBA past president and long-time ARB critic, said Salisbury had done the right thing. 'Ian has bravely attempted to stir porridge,' he said. 'However, I think the whole thing is floored by bad legislation.
'He has only had limited success because nothing short of a full review of the Architects Act will achieve the progress we need,' Hyett added.
Salisbury's decision to stand down was made after the conclusion of the unrelated mediation.
In a separate move, it has emerged that board member Alan Crane has decided not to stand against Humphrey Lloyd for the board's chairmanship. This will leave only Salisbury ally Nick Tweddell to stand against Lloyd.