The treaty was a source of controversy in the last parliament
Eurosceptic MPs will renew calls for a referendum on the Lisbon Treaty when it comes up for debate again in Parliament in the coming weeks.
Conservative MP Douglas Carswell said he and colleagues planned to use a minor technical change to the treaty to trigger a public vote.
This is despite Prime Minister David Cameron ruling out a referendum.
The amendment - expected to be finalised by EU leaders in June - will require ratification at Westminster.
The Foreign Office says it is only a "technical adjustment", rebalancing the number of MEPs between member states.
Mr Carswell, an influential voice on the Eurosceptic right of the party, told BBC One's The Politics Show he remained committed to a public vote.
"Given that we've given an undertaking as a party to hold a referendum if there was any further revision to the European treaties, we need to honour the promises that were made before the election and stick to that, and hold that referendum."
Last November, William Hague - now the foreign secretary - said the Conservatives would not hold a referendum on the treaty.
This prompted accusations from Eurosceptics in his own party and beyond that he had reneged on a "cast iron" guarantee made in 2007.
The Lisbon Treaty, a substitute for the rejected European constitution, is often described as an attempt to streamline EU institutions to make the bloc of 27 states function better.
But its opponents see it as part of a federalist agenda which threatens national sovereignty.
Many people had thought the treaty was all wrapped up when the Czech president signed it last November.
But MEPs have agreed an amendment adjusting the composition of the European Parliament, which held elections last year before the treaty came into force.
The amendment allocates 18 extra MEPs to 12 countries, including one extra MEP for the UK. It will require approval throughout the EU.
In a statement, the Foreign Office said a decision was expected on the changes by the end of the Spanish presidency on 30 June.
"If this protocol is agreed, primary legislation will be needed in the UK to ratify this technical amendment to the Treaty.
"This is a technical change to the Treaty relating to numbers of MEPs and would not transfer any power to the EU."
Edward Macmillan Scott MEP, who defected from the Conservatives to Liberal Democrats, said the prime minister should "slap down" the Eurosceptics in his party.
"They ought to recognise that in government, [Mr] Cameron was going to try and run a serious policy on Europe."
Under the terms of their coalition deal with the Liberal Democrats, the Conservatives have pledged a referendum on any further transfer of powers to Brussels.
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