The fictional heroine Bridget Jones may have expressed her love for Tony and Cherie Blair in the past, but the Tories claimed last night that the chardonnay-swilling singleton was actually one of their own.

David Willetts, the shadow Work and Pensions Secretary, suggested that Ms Jones was "a Tory at heart" because she wanted more than anything to settle down one day in a stable marriage with children.

Mr Willetts' literary appropriation came in a speech reasserting the central importance of marriage in Conservative policy and philosophy. In a move that critics could see as a hardening of Tory policy, he criticised suggestions that the institution was outdated.

Mr Willetts, who is aged 46 and has been married for 16 years, argued that although more people delayed marriage and there were more divorces, marriage remained the best means of combating child poverty and other social ills. But his use of Helen Fielding's character, whose diary was first published in The Independent, is bound to spark the most attention.

In Fielding's latest book, The Edge of Reason, Bridget expresses her joy at Labour winning the 1997 general election. "Hurrah! Could not be more pleased about landslide. That will be one in eye for shaming Tory-Party-Member mother and ex-boyfriend. Har har. Cannot wait to gloat," her diary entry for 2 May reads. "Cherie Blair is fantastic. Tony Blair is the first Prime Minister I can completely imagine having voluntary sex with."

Unfortunately for Mr Blair, Bridget did indicate a possible falling out with the Mr Darcy of Downing Street. "Worry, though, that New Labour will be like having a crush on someone, finally being able to go out with them and then when you have your first row it is cataclysmically awful," she wrote.

Mr Willetts said that real-life Bridget Joneses, young women in metropolitan areas, were in tune with Conservative ideals and values. "She is a Tory at heart because she wants to settle. That doesn't mean her time spent searching for the right man is wasted, but it does mean that she shares our ideas of continuity and the value of marriage," he said.

In a speech to the Policy Exchange think-tank, he rejected views espoused by some Blairite thinkers that people saw marriage as another "lifestyle choice". Marriage was still "the best environment for bringing up children".

Mr Willetts added that the Tories accepted many women had "thoroughly modern attitudes to sex" but said 90 per cent still wanted to get married."We are taking longer to find the right partner, but we are still searching for that person with whom we want to spend the rest of our lives – just ask Bridget Jones," he said.