Prime Minister's Questions: David Cameron v Ed Miliband
David Cameron and Ed Miliband have clashed over Mr Cameron's forthcoming speech on Europe.
Mr Cameron will speak in the Netherlands on Friday and is expected to announce plans for a future referendum on the UK's relationship with the EU.
Labour leader Mr Miliband said a future referendum would "hang a closed sign" around British business.
But the PM said it was right to negotiate a better relationship.
Mr Cameron has faced pressure to hold a referendum on Europe and has been criticised by some in his own party for not doing more to get powers back from the EU to the UK.
In his speech he is expected to support a loosening of the UK's relationship with the EU, to be endorsed by a referendum.
'Divided and weak'
Critics have suggested this could raise the prospect of the UK leaving the EU and harm UK business interests.
Mr Cameron told MPs the "massive changes" taking place in Europe following the eurozone crisis allowed the opportunity for countries to renegotiate a better relationship with Europe.
He said there was now a choice about how to respond: "Do we look at these changes and see what we can do to maximise Britain's national interest and do we consult the public about that, or do we sit back, do nothing and tell the public to go hang?"
But Mr Miliband said the promise of a referendum in five years' time could jeopardise the UK's business prospects and lead to "five years of businesses seeing a closed-for-business sign hanging around Britain".
Mr Cameron insisted that British business backed his policy.
He said: "What business wants in Europe is what I want in Europe - for us to be part of Europe but a more flexible Europe, a more competitive Europe, a Europe that can take on the challenge of the global race and the rise of nations in the south and the east."
He warned that it would be dangerous for Britain to "bury our head in the sand" and pretend there was no debate happening about Europe.
"The most dangerous thing for this country would be to see the changes that are taking place in Europe, because of the single currency, and stand back and say we're going to do nothing about it.
"What Britain should be doing is getting in there, fighting for the changes we want so then we can ask for the consent of the British people to settle this issue once and for all," he said.
Mr Miliband accused the prime minister of losing control of his party. On Europe, he said: "It's the same old Tories; a divided party and a weak prime minister."
But the prime minister blamed Labour's decision to sign up to "treaty after treaty" and its refusal to consult the public on Europe for creating the current situation.
"There will be a very simple choice at the next election. If you want to stay out of the single currency, you vote Conservative. If you want to join the single currency, you vote Labour," he added.
Ahead of Mr Cameron's speech, a group of Conservative backbench MPs has published a report, welcomed by the foreign secretary, calling for a substantial return of powers to the UK from the European Union.
Fresh Start, which says it is backed by more than 100 Tory MPs, wants the UK to remain in the union, but with "significant revisions" to treaties - including the return of control over all social and employment law.
However, Ken Clarke, a veteran pro-European, who attends the cabinet as a minister without portfolio, told the Financial Times that any referendum would be a "gamble" that could lead to the UK leaving the union.
During the exchanges in the Commons, both leaders sent their condolences to the families affected by the helicopter crash in London on Wednesday morning and paid tribute to the quick response of emergency services.
Kate Hoey, MP for Vauxhall where the helicopter crashed, asked the prime minister whether London's changing skyline meant "where and how and why helicopters fly through our central city" needed to be looked at.
The prime minister said he was sure the rules would be looked as part of the investigations into the crash.