PRIME Minister Tony Blair has publicly backed David Blunkett in the face of newspaper reports that his Home Secretary is having an affair with a married mother.

Mr Blunkett has refused to discuss the claims, insisting that his private life has no bearing on the way he carries out his duties.

Last night, the woman was named as Kimberly Fortier, publisher of The Spectator magazine.

The story of the three-year affair was broken yesterday by the News of the World, which did not name Ms Fortier but did carry a picture of her.

The picture, which did not show her face, was taken as she arrived at Mr Blunkett's London home last Wednesday.

A Downing Street spokes-man said: "The Home Secretary's private life is a private matter. The Prime Minister thinks he is doing an excellent job as Home Secretary."

In a statement, Mr Blunkett, 57, who has three sons from his former marriage, said: "After my divorce, I decided not to talk again about my subsequent private life.

"I have stuck to that principle over the years, whatever the pressure to confirm or deny a particular story, and defended all politicians' right to a degree of privacy in their private life.

"I am adhering to this approach now.

"My personal life is my business and has never compromised my jobs as an MP and Cabinet minister.

"Anyone purporting to speak about my private life does so without knowledge or authority."

According to the newspaper, Mr Blunkett and Ms Fortier were introduced in 2001 and have met discreetly in London and in the countryside.

It quoted an unnamed source, said to be close to Ms Fortier, as saying: "In truth, he has been devastated at being unable to lead a normal life with her. He is a man very deeply in love.

"He has one of the busiest diaries in government, but when time allows there are passionate moments.

"None of this rests easily with David. He has a deep conscience. But this is no casual fling. He's totally in love with her. Complete and utter devotion. She is an incredibly bright and vivacious woman."