FORMER British prime minister Lady Thatcher is preparing to publicly denounce the ''treachery'' of leading Tory figures for their part in her downfall. At the top of the list is believed to be Governor Chris Patten, environment secretary in her cabinet and believed to be one of the principal plotters. Lady Thatcher, who was believed to have patched up her differences with Mr Patten, even staying at Government House on her last visit to the territory, is to avenge herself in an explosive series being prepared for British television. Also on the list are Chancellor Kenneth Clarke and Defence Secretary Malcolm Rifkind. The former premier's revenge will come as she describes how ministers were called one by one to her room in the Commons and asked whether they believed she should resign. Her supporters have long regarded the way many cabinet ministers warned her she could not triumph in the second leadership ballot in November 1990 as the dumping of Britain's greatest post-war leader by envious men. Lawyers are combing her accusations which come in a BBC series Thatcher, the Downing Street Years, to be screened in October. She will be heard describing many of her early cabinet colleagues as ''preening'' individuals driven by the ''biblical weakness, vanity'', male chauvinism and class prejudice. She also accuses those party members who did not want her to take the prime ministership in 1979 of ''looking down'' on the ''grocer's daughter''. The programme reveals that she constantly felt the cabinet resented her being a woman and was at war until the last days of her 11-year administration. Producer Denys Blakeway has refused to reveal the names of the ministers. At the time of her downfall, Mr Patten was singled out by Thatcherites for blame. Eighteen months after her downfall there were reports of dancing for joy at Lady Thatcher's London headquarters as the former Bath MP lost his seat in the April 1992 election. he had engineered as party chairman.