The prime minister has been challenged on the performance of the railways under his government.

Quizzed by the Opposition leader, Tony Blair conceded that performance had got worse since the Hatfield crash.

"After the Hatfield rail disaster it was recognised that the state of the rail infrastructure was infinitely worse than we supposed," said Blair.

"That was as a result of years of under-investment in our rail industry which we are now putting right."

The prime minister added that Labour was committed to a massive programme of investment to correct the decades of neglect.

"We are set to double the amount of public and private investment in our railways," said Tony Blair.

"The only way of achieving that better improvement on the railway is for that investment to go in."

But Iain Duncan Smith said one in five trains was now running late and services were worse than when the government came of office.

The Tory leader said the British public was being asked to find a further £58 billion to restore services to the levels inherited by Labour.

"It's another example of taxpayers paying more and getting less," Duncan Smith said.

"Isn't that another reason...why nobody believes a word he says anymore?"