The treaty is intended to replace the failed EU constitution

Britain's "red lines" in the EU treaty negotiations are "unravelling by the day", say the Conservatives.

Ministers say Britain has secured control over human and social rights, foreign policy and tax and benefits.

They argue that the "opt-outs" mean there is no need for a referendum on the draft treaty.

But shadow foreign secretary William Hague said all vetoes, apart from defence could be axed, and opt-outs did not offer sufficient protection.

The new treaty is planned to replace the failed EU constitution, rejected by voters in France and the Netherlands in 2005, and is expected to be finalised later this year.

'Ratchet clause'

The Tories say there should be a referendum because the government had promised one on the constitution, and it is essentially the same thing.

The government argues it is not necessary because Britain's "red lines" have not been crossed.

The red lines are unravelling by the day, every time we get more detail about this   William Hague

But Mr Hague told BBC Radio 4's Today programme that a "ratchet clause" in the draft treaty would allow the EU to extend its powers further in the future, without having to draw up a new treaty.

"All of those vetoes other than over defence can be abolished by agreements between European governments in future, without having to go through the whole process of negotiating a fresh treaty or ratifying that in any formal way," he said.

"The red lines are unravelling by the day, every time we get more detail about this.

"For instance there is a declaration attached to the treaty that is supposed to protect our independence in foreign policy but it now turns out that is not legally binding."

And he said the opt-out on the Charter of Fundamental Rights would only extend to "certain areas of law" and its validity was disputed by the European Court of Justice.

'Quintessentially'

Some Labour MPs also back a referendum - among them former minister Gisela Stuart, who helped draw up the original constitution and says all the its "big items" are preserved in the draft treaty.

But the government has said it has signed up to a "UK version" of the treaty and its opt-outs mean a referendum is unnecessary.

Europe minister Jim Murphy told the BBC: "We wouldn't sign up to any treaty that transferred in any significant way, any UK sovereignty to the European Union."

Prime Minister Gordon Brown has accused the Conservatives of returning to the "old agenda" on Europe. His predecessor Tony Blair, who negotiated the red lines, said the treaty was "quintessentially" in Britain's interests.