Deloitte & Touche's head of professional practices, William Barnes, who specialises in auditing law firms, is to leave next spring without a new job to go to.
Barnes, who is 42 and has been a Deloittes audit partner for 10 years, said that he had only ever wanted to be in audit for "a certain number of years" and that he had agreed with management a year ago that he would leave in the spring.
"I just felt that it was probably time I had a change," he said. "I'm confident enough that something will turn up."
He will be replaced as head of the unit by partner Nigel Llewellyn.
Deloittes audits more law firms than any other of the Big Six accountancy firms, and has so far resisted moving into legal services in the UK.
There had been speculation that Barnes was leaving because the firm was now looking to start providing legal advice, but Barnes denied this, saying: "One of my clients asked about that, but I don't think the firm's position has changed one iota."