The prime minister has defended a large rise in the number of pensioners facing means-tests for state benefits.

Tony Blair's comments came as the Conservative leader attacked the government's policy of forcing more pensioners to go "cap in hand" to the government in order to make ends meet.

"Under his government persistent pensioner poverty has actually risen since 1997," said Duncan Smith. "Now a pensioner couple will have to save £180,000, that's a massive amount, just to escape his means test."

But the prime minister said pensioners were "absolutely delighted" to be on the pensions credit as it provided them with a higher income.

"This government has done a huge amount for the poorest pensioners in our community," he added.

Despite Blair's reassurances the Tory leader said there were now six million pensioners on means-tested benefits.

"That's two million more pensioners than when he came to power in 1997, two million who have to go cap in hand to his government just to make ends meet."

He called on the prime minister to reduce means-testing and raise the state pension "to give pensioners dignity and independence in retirement".

Responding, the prime minister mocked Tory plans to link the state pension to earnings.

"They are the people who took away the link between earnings and pensions," he said. "We make no apology for saying the poorest should get most."

Tory MP Nigel Evans later stepped up the attack on Labour's pensions record. He said the prime minister should "start supporting our pensioners and stop kicking them at every turn".