Cathy Woodhead told The TES: "My only explanation of the peculiar behaviour of (Education Secretary) David Blunkett and his failure to act, is that there is a bond between Tony Blair and Chris."
Despite mounting pressure on Mr Woodhead and intense media interest, the Department for Education and Employment is continuing to back the chief inspector.
The DFEE this week said it had no plans to make an announcement on the future of Mr Woodhead. Mr Blunkett has dismissed the claims as "tittle-tattle", saying he is aware of no evidence that would change the position of the chief inspector.
The controversy arose after Mr Woodhead told trainee teachers at Exeter University that relationships between pupils and teachers could be "educative and experiential". His comments came at an embarrassing time for the Government which was trying to push through legislation outlawing relationships between teachers and pupils aged 16 or 17.
Mr Woodhead's ex-wife then told the Mail on Sunday that he had confessed to the affair with Ms Johnston in April 1976 while he was still a teacher at Gordano school, Portishead.
Mrs Woodhead said this week: "He started this with his remarks at Exeter. All I was doing in my article in the Mail on Sunday was to show he was blatantly lying and it is wrong.
"It is not for me to say whether he is good at his job or not.
"Mr Blunkett talked of my unsubstantiated allegations - I have now, through my solicitor, sent him the statements made at the time of the divorce. Nobody has asked Chris to give his side of the story."
Mrs Woodhead gave a number of interviews this week. On Talk Radio she denied she was part of a left-wing conspiracy to sack the chief inspector.
Mrs Woodhead said this week she would consider suing her former husband who, she says, is effectively calling her a liar.
Former colleagues have alleged the affair was common knowledge in the school.
But Mr Woodhead and Ms Johnston have made sworn statements that their nine-year relationship did not start until they had both left the school.