Deputy Labour leader Harriet Harman warned the Health and Social Care Bill would lead to “fragmentation and privatisation” in the NHS.
Mr Clegg dismissed her call, claiming that Labour had turned its back on reform and refused to commit more money to the health service.
The Bill, which will give GPs and medical professionals in England greater control over NHS budgets, faces a final test in the Lords next week at its third reading.
At their spring conference the Liberal Democrats refused to fully support the Bill and rebel MPs from the party yesterday failed in a bid to kill it off.
Ms Harman said Mr Clegg “obviously thinks he is doing a stunning job” on the NHS.
She asked: “Can you explain why you have failed to persuade the doctors, the nurses, the midwives, the paediatricians, the physicians, the physiotherapists and the patients?”
Mr Clegg told her: “The Labour Party used to believe in reform. Now they believe in starving the NHS of cash.”
Speaker John Bercow was forced to intervene as the noise levels rose in the Chamber, but Mr Clegg continued his attack on Labour, saying the party’s election manifesto had promised “sustained reform”.
He asked: “The Labour Party was right then and is wrong now. What happened?”
Ms Harman said she was “proud” of Labour’s record on the NHS, adding that no-one believed Mr Clegg.
“No wonder you can’t convince those who work in the health service, you can’t even convince your own conference,” she said.
“People are still against this Bill because it hasn’t changed one bit. It’s still a top-down reorganisation, it’s still going to cost the NHS a fortune and it’s still going to lead to fragmentation and privatisation.”
She joked: “It’s clear the Deputy Prime Minister is not going to stand up for the NHS. The only thing he stands up for is when the Prime Minister walks in the room.”
Mr Clegg said Labour spent £250 million on “sweetheart deals with the private sector which didn’t help a single NHS patient”.
Labour had written NHS laws which were a “privatisers’ charter” offering an 11% premium for private providers “to undercut the NHS”.
He asked: “Are you proud of that?”
Ms Harman replied: “We will compare what our government did on the NHS with what your Government is doing any day.
“You say the problem with this Bill is that doctors and nurses just don’t understand it. But the problem is that they do.”
Making her call for the Lib Dems to block the legislation, she told Mr Clegg: “Even at this late stage it’s within your power to stop this Bill.
“Next Monday the Bill reaches its final stage in the House of Lords. There are 90 Lib Dem peers, their votes will decide whether or not this Bill becomes law.
“Will you instruct Shirley Williams and your peers to vote to stop the Bill?”
Mr Clegg said shadow health secretary Andy Burnham had said it would be “irresponsible” to increase NHS spending.
The Deputy Prime Minister said: “They don’t believe in more money for the NHS, we do.”
The Government was making “sweetheart deals” illegal and was making it a requirement to deliver a “more equal outcome” in the NHS.
Ms Harman said Mr Clegg’s response was “absolute rubbish”. She added: “In undermining the NHS and making Shirley Williams vote for it, he has trashed not one but two national treasures.”
She told Mr Clegg: “You didn’t need to sign the Bill, but you did. You could stop the Bill, but you won’t.
“You say the Lib Dems make a difference, but they don’t.
“What has happened to that fine Liberal tradition? They must be turning in their graves.
“The party of William Gladstone, the party of David Lloyd George, now the party of Nick Clegg.”
The Deputy Prime Minister told her: “What we are doing on this side of the House, the two parties which have come together in the coalition, is sort out the banking system which you left in a mess, sort out the public finances which you left in a mess, sort out the economy which you left in a mess, to stop the arbitrary privatisation of the NHS you left in a mess.
“In government the Labour Party ran out of money, in opposition they are running out of ideas.”