Batman is accustomed to taking on eccentric villains such as the Joker, Catwoman and the Penguin. But how will he cope with the self-styled Quiet Man?

Iain Duncan Smith, the former leader of the Conservative Party, has gone on the attack after taking his daughter, 15, to see The Dark Knight, the $150 million (£80m) film starring Christian Bale. The British Board of Film Classification, which awarded the film a 12 Advisory (12A) certificate, has received 82 complaints, a total likely to make it the most controversial release of the year. The certificate means that children younger than 12 may view the film if accompanied by an adult.

In a letter to The Times, Mr Duncan Smith describes the film as “relentlessly violent”. He writes: “I was astonished that the board could have seen fit to allow anyone under the age of 15 to watch the film. Unlike past Batman films, where the villains were somewhat surreal and comical figures, Heath Ledger's Joker is a brilliantly acted but very credible psychopathic killer, who extols the use of knives to kill and disfigure his victims during a reign of urban terrorism laced with torture.”

He and other correspondents to the board have questioned whether it has become too permissive because of pressure from film distributors to allow films to be seen by audiences of a wider age range.

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Even executives at Warner Bros, which distributes the film in Britain, were surprised to receive such lenient treatment. One source contacted by The Times admitted privately that he would not take a ten-year-old child to see it.

The board maintains that 82 complaints is a tiny fraction of the 4.7 million Britons who have been to see the film. Sue Clark, a spokeswoman for the board, said that the film was at the upper limit of the 12A bracket, but that violence was more acceptable because of the superhero context.

The board's website states: “The Dark Knight is a superhero movie and the violence it contains exists within that context, with both Batman and the Joker apparently indestructible, no matter what is thrown at them.”

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