The current turmoil in Europe is an opportunity for the United Kingdom to "refashion" its relationship with Brussels, David Cameron has said.
In a speech in London, the prime minister argued powers should "ebb back" from Brussels to Westminster as part of "fundamental" future reform.
Although the European Union is "out of touch" on many issues, he said it is not in the UK's national interest to exit.
The PM is under pressure from many of his MPs to renegotiate UK membership, the BBC reports.
Some Conservatives want to go further and leave the EU altogether.
The prime minister's authority was directly challenged last month when 81 Tory MPs defied the leadership and voted for a referendum on the UK's continued place in the EU.
Mr. Cameron used a major foreign policy speech in the City of London to argue that the eurozone financial crisis has challenged longstanding assumptions about how the EU should evolve and its 27 members must now ask what kind of union they want in the future.