Michael Portillo will present a feature-length documentary about Margaret Thatcher for the BBC in which friends and foes promise to tell the inside story of her premiership.

David Cameron and Kenneth Clarke are among the figures interviewed for Portillo On Thatcher: The Lady's Not For Spurning, a 90-minute film screened on BBC Four this month.

Once seen as her protege, Mr Portillo discusses Lady Thatcher’s faults and the negative influence she has had on the Conservative party after the crushing 1997 defeat.

He said: “Her power over the party didn’t evaporate when she was dumped as leader. In four subsequent leadership elections she nominated the winning candidate and one by one they fell.”

Kenneth Clarke tells Mr Portillo: “She really didn’t behave well. She never came to terms with it (her forced departure) and she encouraged dissent on a grand scale.”

Recalling the end of her reign, Mr Portillo said: “There was talk that her best days were behind her, that she was being difficult, refusing to listen. Little clouds of doubt were appearing in our Thatcherite skies.”

William Hague, Michael Howard, Norman Lamont and former Thatcher aides including John Whittingdale MP defend the former Prime Minister in the film.

For Mr Portillo, his famous election night defeat in 1997 was partly the result of the internal wounds inflicted by Lady Thatcher’s defenestration.

He says: “The Tories were slaughtered. My defeat, announced at 2am, was symbolic of the rout. My humiliation was later voted the public’s third favourite television moment of the twentieth century. People gleefully asked each other ‘were you still up for Portillo?”.

The film’s title is illustrated by Lady Thatcher’s decision to spurn David Cameron, who failed to court her sufficiently, by appearing in Downing Street alongside Gordon Brown.

The BBC is rediscovering Lady Thatcher, 82. A light-hearted film, Margaret Thatcher – The Long Walk to Finchle, will dramatise her struggle to break into politics, in the face of male-dominated Conservative selection committees.

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