David Cameron has promised to change the law so that no further powers could be transferred to Brussels without the approval of the British people in a referendum.
The Tory leader acknowledged that his campaign for a referendum on the Lisbon Treaty was over after it was signed by all 27 members of the European Union.
But he went on: "We will make sure that this never, ever happens again."
He added: "Never again should it be possible for a British government to transfer power to the European Union without the say of the British people in a referendum."
Mr Cameron said that the Tories' campaign for a UK referendum on the Lisbon Treaty was over after the Czech Republic became the final EU member state to sign the document on Tuesday.
"It's no longer a treaty, it's been incorporated into EU law," he said, adding that the new posts of president and foreign minister were now being created.
"We cannot hold a referendum and magically make those posts or the Lisbon Treaty itself disappear, any more than we could hold a referendum to stop the sun rising in the morning," he went on.
He said that people would "resent" the fact that there would not be the referendum that was promised by Tony Blair and Gordon Brown.
A Conservative government would amend the European Communities Act 1972 to prohibit the transfer of power to the EU without a referendum. That would cover any future attempt to take Britain into the European single currency, he said.
"We will give the British people a referendum lock to which only they should hold the key, a commitment very similar to that which exists in Ireland," Mr Cameron added. "This is a major constitutional development, but I believe it's now the only way to reassure the British people that powers cannot be given away without their explicit approval in a referendum."
Read More
MORE ABOUT