EU leaders are expected to clash at next week's summit
Downing Street has indicated the treaty that emerges from next week's EU summit will not be put to a referendum.
Tony Blair promised a public vote on the EU constitution in 2004 - before it was rejected by France and Holland.
Number 10 said the document expected to be agreed next week would be an "amending" treaty rather than a "constitutional" treaty.
But the Conservatives have said any deal handing power to Brussels must be put to the public in a referendum.
Mr Blair's spokesman said: "We have said this should be a treaty without the characteristics of a constitutional treaty.
"No previous amending treaty has required a referendum."
He said negotiations were continuing but Britain would not accept any proposals that threatened its labour and social security laws.
It would also draw the line at proposals affecting the common law, police and judicial system, foreign and defence policy, including Britain's Security Council seat, and the cost, scope and structure of the social security system.
German Chancellor Angela Merkel, who is chairing next week's EU summit, is pushing for a deal that will preserve the substance of the original constitution document.
This sets up the prospect of a showdown with Mr Blair in what will be his final major engagement before stepping down as prime minister.
Ms Merkel has insisted there is no contradiction between dropping the title "constitution" to allay public fears about radical EU change, while keeping the bulk of the original document.
She wants to steer EU leaders towards a new treaty which will give the EU a "single legal personality" and a legally-binding Charter of Fundamental Rights.
This could give British workers new rights to go on strike.
There is also the prospect of more majority voting including in criminal law and foreign policy - both areas where Mr Blair has pledged to preserve British sovereignty.
An EU "foreign minister" - although with a different title - is still on the cards as well as a full-time post of "European President".
But the summit is not thought to likely to reach a final deal, with the finer details expected to be sorted out an "intergovernmental conference" later this year.
The British, French and Dutch governments have argued that the treaty must be simplified to prevent the need for further referendums.
But Timothy Kirkhope, Conservative MEPs' group leader, insisted the British government must hold a referendum.
He said: "In the event of a transfer of more powers to the European Union the British people should have the right to a referendum.
"No-one under the age of 50 has ever voted on the issue of Europe.
"Conservatives want a referendum focused on the big issues such as globalisation and global poverty, not only the issues of institutional reform.
"We need a referendum, not only on the Europe we want to see, but on the kind of Europe we don't want to see."
The Conservatives' spokesman on Europe, Mark Francois, also warned that the British people had to be allowed a referendum if any further powers were transferred to Brussels.
He said changing the name to downgrade a "constitution" to an "amending treaty" did not remove the obligation to put any new agreement to a public vote.
Liberal Democrat Euro MP Sarah Ludford said progress must be made on a new treaty particularly in the area of EU co-operation on crime and terrorism.
"While the Brussels machine is deadlocked by the search for 27-country unanimity, the terrorists and criminals are free to bomb their way across Europe," she said.
"No British government has ever had the guts to tell the British people that sovereignty means real, shared power to control events rather than the hollow prize of unsplendid isolation."