Cherie Blair to write book about wives at Number 10

As consorts to the most powerful politicians in the land, they have balanced the vital duty of not yawning at diplomatic dinners with other pursuits such as penning verse and, in one case, giving birth to 13 children.

Now, it seems, the latest occupant of the role of Prime Minister's wife is to set a precedent by writing a history of the experiences of women who have taken on the burden – including herself. Cherie Blair is working on a biography of prime ministerial spouses for several months by interviewing former Downing Street insiders.

The book, which she is jointly writing with Cate Haste, wife of the New Labour peer Melvyn Bragg, will be a first venture into print for Mrs Blair beyond her contributions to legal journals in her role as a leading barrister.

Downing Street refused to comment on the book yesterday, saying only that it was a "private matter".

But the claim that the book is to include an account by Mrs Blair of her life at Number 10 attracted criticism for exploiting the grey area between the private and public lives of the Blairs.The Prime Minister's wife has fiercely maintained the privacy of her family, including taking out an injunction against a former nanny, Rosalind Mark, who tried to publish a book about her time with the Blairs.

She has also kept a low profile since last year's "Cheriegate" scandal over her purchase of two flats with the help of a convicted conman during which she spoke of the pressures of being a QC, mother, wife and charity worker, saying: "There just aren't enough hours in the day".

Norman Baker, the Liberal Democrat MP, said: "Once again, it blurs the lines between the political and the private. She has a very privileged position and the book will no doubt be sympathetic to the Labour project."

Mrs Blair is understood to have started work on the book late last year at the height of the row over her dealings with the Australian fraudster Peter Foster, the partner of her friend and spiritual adviser Carole Caplin.

It is claimed that among the string of interviewees Mrs Blair has invited to the family flat in Downing Street is Lady Margaret Colville, the wife of the private secretary to Winston Churchill.

Mrs Blair has previously been criticised for using Downing Street for her private work after she hosted case meetings there with colleagues from her legal chambers.

The Prime Minister's wife will not be short of material for her work. From Elizabeth Wrottesley, second wife of the Duke of Grafton (Prime Minister from 1767 to 1770) and mother of 13 of his 16 children, to Audrey Callaghan, who avoided appearing in public, the role has long required its holders to balance the demands of domestic life with the thrust of politics.

Among the more colourful of recent prime ministerial partners, on whom Mrs Blair is thought to be concentrating, is Mary Wilson, wife of Harold, who acquired a significant public profile through her poetry writing and refusal to live at Number 10, and Clementine Churchill, who was not averse to shaking her head in disagreement when she sat behind her husband on a public platform. Whether or not Dennis Thatcher has been accorded the status of an honorary Number 10 wife is not known.

Neither Mrs Blair nor Ms Haste, who has had several works published including a history of sex in Britain, are thought to have approached a publisher about the project. It is not known whether Mrs Blair plans to profit financially from the book or donate the proceeds to charity.The only precedent for such matters is her immediate predecessor in Downing Street, Norma Major, who kept the royalties from her coffee-table tome on Chequers, the prime minister's country retreat.