The prime minister took advantage of a poor performance by Iain Duncan Smith to successfully negotiate his Commons statement on last week's reshuffle.

Flanked by every senior Cabinet minister, Tony Blair told MPs he was acting to end the "outdated" and "anomalous" position of the lord chancellor.

Scrapping the role of the lord chancellor through the creation of the new Department for Constitutional Affairs was an "essential act of constitutional modernisation", he said.

To Labour cheers and silence from the opposition, the prime minister said he was looking forward to the next general election.

"He wants to fight to the death to keep the minister in charge of our courts system in a full-bottomed wig, eighteenth century breeches, women's tights, sitting on a woolsack rather than running the courts service," he said.

"Well, it says a lot more about the Conservative Party than it does about the Labour Party. If that is the centrepiece of his electoral strategy, roll on the election."

Lord Tebbit, the Tory leader's political mentor, told BBC2's The Daily Politics: "Iain went on too long and asked too many questions. He allowed the prime minister to get away with it."

A Tory MP told today's Independent that Duncan Smith "could not have done any worse".