At the launch of his new book* in London, Mansell nominated the team's test driver, Damon Hill, as a worthy candidate to take his place.
He also said he wanted to put the record straight and ensure the public was not misinformed over the circumstances of his split with Williams and his announcement that he intended to retire from grand prix racing at the end of this season.
Mansell said: 'The force behind me has always been the public and I will not have them misinformed. Why negotiations broke down was that after Hungary, where I believed an agreement had been struck, I regrettably received a call from Sheridan Thynne to say that everything that had been agreed had been taken away totally.' He said the talks in Hungary had been witnessed by his wife Rosanne, who was at his side last night. He was also flanked by his lawyer.
Mansell went on: 'Within one or two hours of the call that evening, Mr Sheridan Thynne resigned.' Thynne, a long-time friend of Williams, has been responsible for putting together the sponsorship deals which fund the team operation. Williams have a budget of between pounds 20m and pounds 30m a year.
Mansell said it was Thynne who was responsible for negotiating the deal that took him back to Williams two years ago and he had again been the intermediary this time. Thynne said he had been advised by his lawyer not to comment.
Mansell said: 'It has been said that my team wanted Mansell and then Alain Prost, and not Prost and Mansell. Why, then, is it that Prost signed, at the latest, in April this year?
'I would suggest it was the other way round. I want to put this to bed, it's history. I want to leave Formula One with my head held high and I want to thank Williams. Unfortunately, I wasn't the favoured one.
'Mr Williams told you all he had no support or sponsorship from this country and therefore his consideration would have to come from where he gets the most money. That is why Mr Prost is in the car.'
Hill and Martin Brundle are said to be on Williams' shortlist for next year. Mansell said: 'My personal feeling is that Damon deserves the chance. He knows the car and he'd do a good job. If Martin got it, great. As long as it's a Brit, I'll be happy.'
*Mansell and Williams, The Challenge For The Championship, by Nigel Mansell and Derick Allsop, published by Weidenfeld and Nicolson, pounds 20.Reuse content