Tory leader David Cameron says the "crisis" in the criminal justice system and health service is a symptom of a government "that has been paralysed".
Mr Blair was questioned over his departure date
In rowdy Commons exchanges he asked Tony Blair to say why he "does not trust" Chancellor Gordon Brown to take over from him now as prime minister.
"Isn't it becoming increasingly clear that you should go and go soon?"
Mr Blair said he would not debate his departure with him, joking there were "enough lining up to do that already".
The prime minister has said he will not contest a fourth general election - which is expected in 2009, but which must be held by May 2010.
This week he went further, assuring rebellious Labour MPs he would ensure his successor has "ample" chance to establish themselves before the next election.
Former minister John Denham has said Mr Blair was increasingly out of touch and Labour cannot afford another year of "division and drift".
After a troubled fortnight, Mr Blair won supportive words from his old friend ex-US President Bill Clinton on Wednesday night.
Mr Clinton told political and business leaders in Glasgow: "Whatever political problems the government are in, the UK is way better off than it would have been had it not been governed the way it has for the last 10 years."
Earler, in the Commons, Mr Blair answered Mr Cameron's attack by pointing out he had won a general election just a year ago.
He claimed the only policies the Conservative leader had were on children's clothes and chocolate oranges - a reference to recent speeches by Mr Cameron attacking different aspects of consumerism.
Mr Cameron hit back, saying that only a week ago Mr Blair had been saying he would be serving a full third term.,
He asked: "What changed your mind?"
Mr Blair replied: "I have no intention of debating that with you. Frankly, there are probably enough lining up to do that already."
'Time to go'?
He said "policy" was the one thing the Tory leader did not want to talk about and it was policy which would determine his government's future.
But Mr Cameron said the issue of how long Mr Blair remained in office was of "clear public interest".
"Could you unravel a mystery for us - why don't you trust the chancellor to take over the government now?" he said.
Mr Blair side-stepped the question, saying he had seen off four previous Tory leaders who had called for his departure.
Mr Blair said it was important for his government to deliver the manifesto on which it stood at the general election, unlike Mr Cameron, who "doesn't stand by a word" of the manifesto he wrote for his party.
Tory John Maples also criticised the prime minister over his decision to take away the Deputy Prime Minister John Prescott's department in last week's reshuffle, but not his title, salary or perks.
Mr Maples joked: "You are right - it's better to pay the deputy prime minister for not running a department, than to pay him for running one," he said.
Mr Blair responded that he preferred "Prezza to Hezza", joking that two years after Michael Heseltine was appointed as Tory deputy prime minister, the party suffered "the worst election result in the Tories' history".
Meanwhile ex-minister Claire Short told BBC 2's Daily Politics she thought new Home Secretary John Reid, or his predecessor Charles Clarke, might stand against Mr Brown for the right to succeed Mr Blair.