John Major was a "ghastly" prime minister and the Conservative Party would have been much better off if he had lost the 1992 general election, according to the late Sir Denis Thatcher.

In an interview to be screened on Channel 4 this Sunday, Sir Denis attacked the "treachery" of senior Conservatives who brought about his wife's downfall 13 years ago.

Interviewed by his daughter Carol last October, Sir Denis said: "If Major had lost, we wouldn't have had the disaster we've got now.

"He was a ghastly prime minister, more people deserted our party.

"The whole of the situation of the Conservative Party today springs from that night when they dismissed the best prime minister the country had had since Churchill."