The EU treaty is "substantially equivalent" to the EU Constitution thrown out by Dutch and French voters in 2005, MPs have said.
EU leaders are due to sign the reform treaty later this month
The European scrutiny committee said it should be "made clear" the UK can keep opt-outs of parts of the document.
The Conservatives said the government was now "morally bound" to hold a referendum on the treaty, as had been promised on the constitution.
But ministers say the two documents are "substantially" different.
The treaty incorporates some of the old EU Constitution, on which Labour had promised a referendum before it was scuppered by the Dutch and French votes.
The Conservatives argue it is as much as 90% the same.
But the government says it has secured opt-outs or "red lines" - in areas such as human rights, tax and benefits, foreign policy and justice - which makes it different.
Prime Minister Gordon Brown has said he will veto the treaty if these are not kept.
The committee criticised the "essentially secret" drafting of the document, which is due to be signed by EU heads of government in Portugal after an Intergovernmental Committee (IGC) later this month.
It said the treaty had been drawn up hastily, with draft texts available to member governments only 48 hours before the IGC in June.
This had been carried out "by the [EU] Presidency, with texts produced at the last moment before pressing for an agreement", it said.
The report said: "The compressed timetable now proposed, having regard to the sitting terms of national parliaments, could not have been better designed to marginalise their role."
The report said it was "likely to be misleading" for the government to claim that the treaty did not have the same characteristics as the constitution.
And it warned that the UK's "red lines" may not prove effective.
In addition, a requirement for national parliaments to contribute to "the good functioning of the Union" may contradict the Bill of Rights, which protects the UK's Parliament from being placed under legal obligations by any outside body, the MPs said.
Mr Brown is being urged to hold a referendum
They added: "In our view, the imposition of such a legal duty on the Parliament of this country is objectionable as a matter of principle and must be resisted."
The report also said: "What matters is whether the new treaty produces an effect which is substantially equivalent to the constitutional treaty.
"We consider that, for those countries which have not requested derogations or opt-outs from the full range of agreements in the treaty, it does."
New provisions to allow national parliaments to object to measures proposed by the unelected European Commission "add very little by way of democratic control over the Commission and the EU institutions", the committee said.
Conservative Europe spokesman Mark Francois said: "It is now crystal clear that the two documents are essentially the same and therefore Gordon Brown is morally bound to offer the people of the country the referendum he promised them."
Derek Scott, chairman of the I Want a Referendum campaign, said: "This report blows a huge hole in the case against a referendum."
Neil O'Brien, director of the Eurosceptic think-tank Open Europe, said: "For a committee which is dominated by Labour MPs to come out and say that this is substantially the same as the European Constitution is really very striking."
He told BBC Radio 4's Today programme the "big turning point" was the doubt cast by the committee on the government's claim that its "red-lines" would protect the UK from the worst effects of the constitution.
"It is going to become very difficult for Gordon Brown to say this is a completely different document."
But Europe Minister Jim Murphy said: "The reform treaty is significantly different to the old constitutional treaty in intent, form and substance."
An alternative report tabled by Conservative committee member Bill Cash, stating that the treaty "requires a referendum of the electorate of the United Kingdom", was defeated.