Wyatt and the mysterious memoirs even his widow cannot read

They run to some three million words and have already made public juicy details of the private lives and beliefs of figures from the Queen Mother to Rupert Murdoch.

But the diaries of Woodrow Wyatt, the former Labour MP turned claret-quaffing doyen of high Tory socialites and assorted glitterati, seem to be a closed book when it comes to his own family. His widow, Verushka Wyatt, revealed yesterday that she has been prevented from reading the unedited text of the famously indiscreet chronicles of the ruling classes in the 1980s and 1990s.

The original handwritten diaries, which revealed the Queen Mother's liking for Margaret Thatcher and Norman Lamont's concern about looking overweight in his swimming costume, are held by Lord Wyatt of Weeford's publisher, Macmillan.

Some three volumes of the diaries, running to more than 2,000 pages, have already been published since Lord Wyatt's death in 1997, prompting at least one critic to complain that their journalist author had filed too much material.

But Lady Wyatt claimed she had been barred from seeing some 300,000 words which remain in the vaults of Macmillan's London headquarters because they may form the basis for yet another volume.

Lady Wyatt said: "[Macmillan] say they might want to publish them. But what harm would it do to let me see them? I could go into their office and read them and not take a copy away. I could sign a confidentiality agreement. But they are just completely unreasonable and refuse even after all this time. It is very upsetting."

Macmillan, the German-owned publishing giant whose authors range from V S Naipaul to the BBC's John Simpson, declined to comment. But it is thought that the company may be sticking to the letter of its agreement with Lord Wyatt that his family - Lady Wyatt and his daughter, the journalist Petronella Wyatt - should not know the contents of his diaries until they were published.

For a dynasty which has made a profession of knowing the details of other people's lives, the stand-off is strange. Lady Wyatt, a Hungarian-born aristocrat, has previously said she had no interest in her husband's diaries, written throughout a career which ranged from his role as a junior minister in Clement Attlee's 1951 government to a 21-year stint as chairman of the Tote racing board. The contents of the unpublished 300,000 words are unknown, but Lord Wyatt made a point of hobnobbing with highest in the land, turning his £2m north London home into a salon attended by prime ministers and royalty.

Lady Wyatt has proved herself adept at handling the media. Last year, she played an instrumental role in the revelation of an affair between her daughter and the Conservative MP Boris Johnson, when he was editor of The Spectator. Lady Wyatt revealed the details of the relationship to a Sunday newspaper after Mr Johnson had dismissed claims of an affair as "an inverted pyramid of piffle". The outraged mother declared that her daughter had an abortion after Mr Johnson, who stepped down from his role as Conservative arts spokesman within days, had promised to marry her only to end the relationship.

Such revelations would not have looked out of place in the pages of the diaries of Lord Wyatt, who described his journals as the "only memorial I can ever leave". The peer, who supposedly ordered the publication of the works to provide a nest egg for his family after his death, created controversy when he broke with convention to detail conversations with the Queen Mother during lunches at which he mixed her gin martinis.

The diaries themselves have been criticised as self-regarding and repetitious, making Lady Wyatt's insistence on reading the contents of the missing 300,000 words all the more intriguing.