A Cabinet Minister could face legal action by Britain’s leading human rights campaigner over allegations that he smeared her by making suggestive remarks about her relationship with David Davis.

Shami Chakrabarti, the director of Liberty, has taken the extraordinary step of threatening to sue Andy Burnham, the Culture Secretary, and demanding that he issue a written apology.

This follows an interview by Mr Burnham to the Blairite Progress magazine, in which he said that he found something “very curious in the man who was, and still is I believe, an exponent of capital punishment having late night, handwringing, heart-melting phone calls with Shami Chakrabarti”. Ms Chakrabarti and Mr Davis believe that the reference to late night “heart-melting” conversations were Mr Burnham’s attempt to hint at an improper relationship. He vehemently denies the suggestion.

Ms Chakrabarti and Mr Davis are both married with children and both say that they have taken offence. Ms Chakrabarti married Martyn Hopper, a partner in the City law firm Herbert Smith, 13 years ago and the couple have a son, aged 6. Mr Davis has been married to his wife, Doreen, for almost 35 years and they have three children.

Mr Burnham’s remarks came after a number of comments highlighting how Ms Chakrabarti, a high-profile civil rights campaigner, and Mr Davis, a right-wing supporter of capital punishment, had worked together on the campaign against the 42-day proposal on detaining terror suspects without trial. The remarks were the last straw for Ms Chakrabarti, 39, who is said to be distraught.

She wrote to Mr Burnham yesterday, with copies to the Prime Minister and Baroness Scotland of Asthal, QC, the Attorney-General, demanding that he apologise publicly. She accused the Blairite Cabinet minister of debasing his office and of setting out to “smear my dealings with the former Shadow Home Secretary”.

In her strongly worded letter, Ms Chakrabarti said: “I must say that I find this behaviour curious, coming as it does from a Cabinet minister; let alone someone with a partner and family of his own.” The letter continued: “By your comments you debase not only a great office of State but the vital debate about fundamental rights and freedoms in this country. Indeed, you seem reluctant to engage in that debate except in this tawdry fashion.”

It added: “I look forward to your written apology as I am sure does Mrs Davis. If on the other hand you choose to continue down the path of innuendo and attempted character assassination, you will find that the privileged legal protection of the Parliament chamber does not extend to slurs made in the wider public domain.”

Aides insisted that Mr Burnham had not intended any smear in the comments, but stopped short of issuing a full public apology or say whether he was writing to Ms Chakrabarti to apologise. A spokesperson said last night: “Andy Burnham was making a political point about David Davis’s inconsistent views on capital punishment and civil liberties. An interpretation has been placed on Andy’s remarks that he did not intend. His comments related to politics and nothing else. He regrets if any personal offence has been caused.”

Ms Chakrabarti is understood not to have been satisfied by this statement.

Mr Burnham was criticised immediately by women Labour MPs. Diane Abbott said: “I am extremely disappointed in Andy Burnham. I thought the Labour Party had left these sort of politics behind. He wouldn’t talk like that if the head of Liberty was a man.”

Karen Buck, a Labour member of the Home Affairs Select Committee, said that the comment was unwise, but added: “I don’t believe he was intending to be personally wounding or politically undermining her.”

Head to head

Shami Chakrabarti She is regarded as one of the most effective lobbyists to walk the corridors of Westminster. Ms Charabarti, 39, was born in London in 1969 to Indian parents. She was educated at a girls’ comprehensive and sixth-form college in northwest London and studied law at the London School of Economics. She was called to the Bar in 1994 and became a lawyer for the Home Office in 1996. She cites J. K. Rowling as one of her heroes because of her ability to teach children the difference between right and wrong. Ms Chakrabarti joined Liberty in 2001 and became its director in 2003.

Andy Burnham The son of a telephone engineer, Andy Burnham was born in Liverpool in 1970. He was educated at St Aelred’s Roman Catholic High School in Newton-le-Willows before going on to Fitzwilliam College, Cambridge, where he gained an MA in English.

He joined the Labour Party at the age of 14 and became a researcher for Tessa Jowell ten years later. In 1998, Chris Smith, the Sports Minister, drew on the Everton fan’s sporting knowledge and made him his special adviser, a position he kept until he was elected MP for Leigh in 2001. Gordon Brown promoted him to the Cabinet last year.

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