Prime Minister David Cameron has insisted he put Britain's interests first by using a veto to avoid signing up to a new European economic treaty.
Mr Cameron has come under fire for leaving the UK isolated while other European Union nations agreed on a new treaty towards closer fiscal union to preserve the euro.
As a result of the veto, 38 years after joining the European Economic Community, Britain has now taken a big step away from a greater Europe.
After 11 hours of bad-tempered talks in Brussels, Britain has been left standing alone on shaky ground as the other EU members forged on ahead.
Mr Cameron told Sky News political editor Adam Boulton: "I said to the people of Britain if I couldn't get a treaty that was good for Britain I wouldn't sign up to it. And I was good to my word.
"What I have done is made sure Britain's national interest is protected. We have the right deal for Britain in Europe."
Mr Cameron acknowledged that it was unprecedented for a British Prime Minister to veto an EU treaty but insisted he was given no choice.
"You've never seen Britain say 'no' to a European treaty before. There was a treaty on the table, it didn't adequately protect Britain's interests," he told Sky News.
"Instead of going along with it, I said no to it. I thought that's my job."
German Chancellor Angela Merkel , speaking near the end of the two-day summit to save the single currency, confirmed the plan to move forward without Britain.
"We have achieved a major breakthrough over the past two days. We are going to implement a new commitment," Mrs Merkel said.
"One country has expressed a clear wish to distance itself, and that is Britain."
Mrs Merkel said the UK has been an important and constructive EU partner over the past two decaded.
She added: "It is quite clear that Britain relies, as we do, on a stable Europe."
It is now expected at least 23 out of the 27 EU countries, led by Germany and France, will aim to reach a treaty deal by March.
The Czech Republic, Sweden and Hungary are also expected to agree to the changes, leaving Britain as the sole dissenter.
Mr Cameron resisted the plans because they might hamper the City of London's ability to attract vital business.
Roughly 10% of Britain's GDP and 11.2% of its tax take comes from the financial sector.
French President Nicolas Sarkozy had earlier insisted the Prime Minister's demands for concessions to protect Britain's financial sector were "unacceptable".
Mr Sarkozy cited lax regulations as a key factor in creating the crisis in the first place.
Mrs Merkel added: "David Cameron was at the negotiating table with us, we made this decision. We couldn't make a lousy compromise for the euro but we had to set up hard rules."
A leading Germany current affairs magazine, Der Spiegel, titled a commentary on the deal 'Bye Bye Britain' .
But Mr Cameron insisted the decision to create a new, separate treaty instead of being able to forge a "treaty within a treaty" did not leave Britain isolated.
"We are not being excluded. We are a leading member of the union," he told Sky News.
"We are the leading member of Nato. It is right for Britain to protect her national interest."
Mr Cameron's defiant stance drew wide support from eurosceptic Tory MPs who said he had succeeded in protecting the City of London.
However, many observers believe a powerful "inner core" of countries will effectively exclude the UK from crucial finance-related discussions and decisions in future.
Some Liberal Democrats and opposition figures attacked the veto as isolationist, with Labour's former foreign secretary David Miliband tweeting: "UK jumped into rowing boat... next to (the EU) supertanker. That is weakness not strength."
Labour leader Ed Miliband said: "Will the UK have a seat at the table when vital economic decisions are taken?
"Have we now got the two speed Europe Britain has always opposed, but without any of the safeguards the Prime Minister promised to deliver?"
Deputy Prime Minister Nick Clegg insisted Britain had only made modest and reasonable demands at the EU summit.
"There were no demands of repatriation of powers from the EU to Britain and no demands for a unilateral carve-out of UK financial services."