UK to keep EU waiting on legal demands

“We don't want to be excessively prescriptive at the beginning of the discussion. This letter is not the end of the process. It is the beginning of the process,” he said.

The UK has previously called for excising the phrase “ever closer union” from the treaty, curbing welfare rights for EU migrants, ringfencing the City of London from eurozone policies, and boosting the powers of national parliaments.

In an allusion to the treaty change idea, Hammond said the UK will seek “substantive legally-binding change” by the end of the process, adding that “[British people] will not be fobbed off with a set of cosmetic alterations to the way the EU works.”

He added, in a conciliatory tone: “If we were not in the EU we would have to find a different way of promoting our economy. It is not impossible but it would be challenging.”

The British PM, David Cameron, in a speech also on Tuesday, is to shed a little more light on London’s thinking.

According to excerpts of his address, leaked to several British media over the weekend, he will call the in/out referendum, due by 2017, “a huge decision for our country, perhaps the biggest we will make in our lifetimes."

He will rule out further votes, describing the poll as Britain’s “final decision.”

He will also threaten to campaign for a No unless he gets what he wants, adding: “If we can't reach such an agreement, and if Britain's concerns were to be met with a deaf ear, which I do not believe will happen, then we will have to think again about whether this European Union is right for us.”

“As I have said before - I rule nothing out. Those who believe we should stay in the EU at all costs need to explain why Britain should accept the status quo. I am clear that there are real problems with this.”

But he will defend the EU on political grounds, instead of only in economic terms, as previously.

“Today, as we confront fresh threats and dangers to our country, I am in no doubt that for Britain the European question is not just a matter of economic security, but of national security too – not just a matter of jobs and trade but of the safety and security of our nation,” the PM is to say.

For its part, the Open Europe think tank in London, over the weekend published new research indicating which EU capitals are likely to sign up to British ideas.

It sees little strong opposition to treaty change, incuding in France and Germany, but does foresee Spanish and Belgian grumbling on the issue.

It believes France will be the most sceptical on City of London safeguards.

It says Spain and Belgium are firmly against greater roles for national assemblies, however.

It also says Poland, the Czech Republic, and Lithuania are likely to vigorously oppose limiting EU migrants’ welfare access.