Foreign Secretary David Miliband has denied giving in to EU "bullying" and has told MPs that UK demands for the new treaty have been "respected".
David Miliband insists that Britain will keep the right to decide its own policy in key areas
He was repeatedly challenged by members of the European Scrutiny Committee about Britain's so-called "red lines".
Tory MP James Clappison said they were "in tatters" and suggested someone had been "asleep at the wheel".
Mr Miliband clashed with committee chairman Michael Connarty who appeared to compare him to Neville Chamberlain.
On Thursday PM Gordon Brown will attend an EU summit in Lisbon, where the treaty's text will be finalised.
The reform treaty will replace the failed EU Constitution, rejected by Dutch and French voters in 2005 - on which the government had promised a referendum.
But the government has said there is no need for a referendum on the treaty, because it has secured opt-outs in key areas such as human rights, tax and benefits, foreign policy and justice.
Mr Miliband was given a two-hour grilling by members of the committee - telling them he was satisfied the EU reform treaty - "respects Britain's red lines".
But the Tories have said the government's powers over criminal justice would be "eroded" because the European Court of Justice had the power to overturn British decisions.
Mr Miliband repeated his view that the protocol on the charter of fundamental rights would not allow the ECJ to override British laws.
"We have a blanket ordinance there that the charter shall not extend the reach of European courts into British law," he said.
'Cut to the quick'
But committee member Mr Clappison told him: "The red lines are in tatters - and for you to agree to something like this and get nothing in return suggests to me that somewhere along the line someone has been, quite frankly, asleep at the wheel."
The committee's Labour chairman, Michael Connarty, also angered Mr Miliband by commenting: "I have visions of peace in our time".
Mr Miliband responded angrily that he had been "cut to my absolute quick" by the remark.
"You are saying this is the equivalent of Neville Chamberlain coming back in the late 1930s from Munich claiming to have an agreement with Adolf Hitler. That is not worthy of any of you."
Mr Connarty said Mr Miliband had "a highly sensitive imagination" but added: "If you're offended by that, then that's your sensitivity and I apologise for saying it if it hurt your sensitivity."
Later he told BBC Radio 4's PM programme the committee had not been convinced, and that the conditions behind Britain's "red lines" had changed "irrevocably".
Last week the European scrutiny committee published a report which concluded that the reform treaty was "substantially equivalent" to the failed constitution.