Sereny said Peter Harris, the Official Solicitor, was informed of the project and told her to keep it "very, very quiet" in order to protect Bell's daughter, who knew nothing of her mother's past. It was this instruction that Sereny claimed stopped her contacting the families of the two boys, Brian Howe and Martin Brown, killed by Bell when she was aged 11.
Mr Harris, who also provoked a storm of protest when he sanctioned a book on mass murderer Fred West, also had talks with Bell herself. The first copies of Sereny's book, Cries Unheard, arrived in bookshops over the weekend, although it is not officially published until this week.
A spokesman for the Lord's Chancellor's Department said: "Mr Harris is able to confirm that he spoke with Mary Bell a couple of years ago about the publication of a book. But the content of that conversation is confidential."
Mr Harris was acting as the official with responsibility for Bell's daughter, who is a ward of court. But the spokesman said Mr Harris was "not dutybound" to pass details of his discussions to the Home Secretary.
Jack Straw, the current Home Secretary, has begun an inquiry into why Home Office officials failed to inform ministers about the book project when they learnt about it two years ago.
The families of Bell's victims have condemned the book deal, for which Bell was paid a sum believed to be around pounds 15,000. Families of the victims of Fred West similarly condemned the deal approved by Mr Harris for West's official life story to be written with proceeds shared among his children.
The Official Solicitor's role includes representing adults incapable of managing their own affairs and children under threat.
As the Bell row rumbled on yesterday, new fears for the future of her 14-year-old daughter emerged with the possibility of her being identified on the Internet.
Although a High Court injunction, taken out in 1984 shortly after the girl was born, prevents the British media from publishing Bell's new name or any details which could lead to identification of her daughter, the law gives no protection against reports on the World Wide Web where publication of the book has inevitably created intense interest.
Ministers who are already examining cases involving Internet breaches of court identification rulings, spent the weekend looking at ways of preventing the girl's name being made public.
But Whitehall officials privately believe it is inevitable that Bell's daughter will be named, if not by an Internet user then by a foreign-based newspaper.
When William Straw, the 17-year-old son of the Home Secretary, was charged earlier this year with possession of cannabis, his identity was widely known among reporters who were prevented by law from publishing the information.
But his identity became common currency among Web users well before the Home Secretary went public on the issue.
Bell, along with her partner and daughter, has been changing address every couple of years in an effort to maintain anonymity.
But when tabloid newspapers tracked her down, the secret that she had kept from her daughter and neighbours was out.Reuse content