Liar: the politicians’ ultimate weapon

Should it be acceptable to accuse a fellow politician of telling a lie? Twice last week, on the subject of public spending, senior politicians have done just that: Lord Mandelson had claimed that George Osborne was telling "deliberate untruths" and David Cameron had accused Gordon Brown of "deceit, dishonesty and deception".

The topic was discussed on the Today programme by Daily Mail columnist Quentin Letts, and former Labour MP Tam Dalyell, who, famously, was twice suspended from the Commons for accusing Margaret Thatcher of lying. Once during the Falklands war over the sinking of the Belgrano, and another time about the Westland affair, when Britain's last helicopter manufacturer was on the brink.

Presenter John Humphrys asked Dalyell if he thought it was wrong for him to be suspended and whether he regretted it.

"No. Those were the rules at the time," he answered, "One doesn't talk about lying of other people either lightly or on trivial grounds. It doesn't enhance one's own prospects, if I can put it that way. But I do think it was the right thing to do."

"Should they be allowed to call each other liars?" Humphrys asked Letts.

"I don't think they should," he responded. "I take the view that Parliament is a high court and to lie there should be the equivalent of perjury. The more casually you make that accusation the less shocking the crime itself becomes. Now when Tam Dalyell laid that charge, probably accurately, at Mrs Thatcher it was a sensation but if that happened time and time again then it would become less of a sensation..."

Parliament, Letts said, should be about "the archaeology of policy formation", but he conceded that it was also about theatre. "It's a very difficult balance but I think we have reached the point currently at Prime Minister's Questions where David Cameron is traducing it.

"I think the vituperation is going a bit too far. It's quite entertaining and brings Parliament to life in some ways but it is also deadening the idea of argument and Parliament should be about argument and about truth. If you are just calling the other person a liar it rather gets blunted by that."

"You say David Cameron is probably going too far at the moment. What would stop him?"

"I would give him fewer questions at Prime Minister's Questions - he has I think six at the moment. I would knock him down to two or three. I think PMQs should be more about the backbenchers. He has too many goes. And he gets bored. If I was advising the new Speaker at the Commons I would say jump in there and stop him, don't give him so many goes, just stop him calling the Prime Minister names."