London: The best-selling author of a short story imagining the assassination of Margaret Thatcher has claimed the former prime minister would have approved of the piece.

Dame Hilary Mantel admitted yesterday that critics were “foaming at the mouth” over her latest work, which depicts an IRA hit man shooting dead the then Mrs Thatcher in the 1980s.

But she refused to apologise, claiming the former Conservative leader would not have wanted her to “shrink” from the topic.

The short story, which led to calls for police intervention over its “sick and perverted” content, was inspired by the writer’s own fantasy about murdering the prime minister.

Looking out from a window in 1983, she saw Mrs Thatcher as she recuperated from surgery in a hospital garden. According to a Guardian interview, published with the short story on Saturday, Dame Hilary’s “finger and thumb [were] forming a gun” as she told the newspaper: “Immediately your eye measures the distance. I thought, if I wasn’t me, if I was someone else, she’d be dead.”

The 62-year-old, made a dame this year, has provoked fury across the political spectrum. But yesterday she said: “The Iron Lady was not afraid of strong opinions and did not shrink from speaking her mind, and would not expect a writer of fiction to shrink either.”

The row comes after Dame Hilary caused offence last year, describing the Duchess of Cambridge as a “shop window mannequin” whose “only point and purpose” is to give birth. She later said her words were taken out of context.

The Assassination of Margaret Thatcher depicts an affluent woman allowing an IRA killer into her flat, so he can shoot the prime minister from a window when she leaves hospital after eye surgery. The characters describe her as ‘cruel” and ‘wicked”, and “rejoice” in her death.

Dame Hilary told the Guardian she feels “boiling detestation” for the politician, who died last year, calling her an antifeminist “psychological transvestite” who did “long-standing damage” to the UK.

But for the majority of her time in power, the author was not even in the country.

For most of the late 1970s and 1980s, Dame Hilary lived in Africa and the Middle East. She and her husband left in 1977 — two years before Mrs Thatcher took office — and reportedly lived in Botswana for five years.

Following a brief time back in the UK they moved to Saudi Arabia in 1983, and did not return until 1986, after the Falklands war and miners’ strike.

But the Wolf Hall writer remained defiant at the Budleigh Salterton Literary Festival, in Devon, yesterday and the event’s marketing claimed her story was `bold, brilliant and transgressive’. One fan who attended said: “She did not seem bothered by all the controversy at all.”

The author told the Guardian she did not consider herself to be either of the characters in the story but was “standing by the window with the notebook”.

She added: “As a citizen I suffered from [Baroness Thatcher], but as a writer I benefited”.

Lord Tebbit, a minister in the Thatcher government from 1981 to 1987, said the piece showed Dame Hilary was “sick and perverted”.

Tim Bell, Baroness Thatcher’s friend and former adviser, told the Sunday Times: “If somebody admits they want to assassinate somebody, surely the police should investigate. This is in unquestionably bad taste.

Smiths singer Morrissey was quizzed by Scotland Yard over his 1980s song Margaret, which described the leader’s death as a “wonderful dream”.

Her daughter Carol, 61, has chosen not to read the piece.