The current turmoil in Europe is an opportunity for the UK 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 EU 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.
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.