The Conservatives say there should be a referendum on the treaty
The Lisbon Treaty would have no major impact on UK sovereignty, says an influential committee of peers.
Ahead of a debate on the treaty next week, the Lords constitution committee said it would have "no constitutional implications" for UK citizenship.
But it said Parliament should get the final say on "opt ins" to controversial parts of the document.
The EU (Amendment) Bill, which would ratify the treaty, has cleared the Commons despite Tory opposition.
The Lisbon Treaty was drawn up to replace the EU constitution, after that was rejected by French and Dutch voters in 2005.
The Conservatives say it should be subject to a referendum, as one was promised on the constitution which they say was fundamentally the same.
But the government says the treaty is very different and does not have significant constitutional implications.
In its report on the impact of the treaty on the UK constitution, the committee said it offered "greater clarity" over where the EU's powers stopped.
"We conclude that the Lisbon treaty would make no alteration to the current relationship between the principles of primacy of European law and parliamentary sovereignty," it said.
"The introduction of a provision explicitly confirming member states' right to withdraw from the EU underlines the point that the UK only remains bound by EU law as long as Parliament chooses to remain in the union."
It says new arrangements concerning the European Convention on Human Rights and Charter of Fundamental Rights would have no significant impact.
But committee chairman Lord Goodlad said: "The committee believes that it is essential for Parliament to be given a veto over the government's use of the UK's power to opt in or opt out of particular EU measures, because use of these powers will affect the final impact of the Lisbon Treaty on the UK."
He said the EU (Amendment) Bill would give Parliament "added powers" over future changes to the way EU affairs are run but said there were concerns about "the frequency with which the rules underpinning the EU are changed".
He asked the government to ensure that no further major amendments to the treaties were made in the near future.
Last year MPs on the European scrutiny committee said the EU treaty was "substantially equivalent" to the rejected EU Constitution.