Voters should be "in no doubt" they will be offered a "real choice" on Europe at the next election, the Prime Minister has said.
David Cameron said any vote would happen within five years but refused to be drawn on whether a poll would include the question whether the United Kingdom should remain in the European Union.
He said the Government was currently reviewing which powers should be repatriated back to Westminster, claiming the EU working time directive should never have been implemented.
"There is going to be a large negotiation in Europe," he told BBC One's Andrew Marr Show. "When I became Prime Minister, people said to me 'Don't worry, the one thing you won't have is any treaty changes in Europe'.
"I think we have already had three. One we vetoed so we aren't involved in at all... and we have had two others. People should be in no doubt that the Conservatives will be offering at the next election a real choice and a real way giving consent to that choice."
Asked whether any vote could be delayed by five or 10 years, Mr Cameron said: "No, no, that's not going to happen."
The Prime Minister was then asked about his previous description of UK Independence Party members as "fruitcakes, loonies and closet racists".
Mr Cameron added: "There are some pretty odd people."
Speaking to Dermot Murnaghan on Sky News, Ukip's leader Nigel Farage hit back.
He said: "It shows how disconnected he is. If he wants to go on being rude about me and rude about Ukip well let him do it, we won't lose any sleep over it.
"I don't think there is any prospect of any deal with the Conservative Party all the while that man leads it, given the way he has behaved and his attitude towards us.
"Look, I would do a deal with the devil if it got us what we need, which is a free and fair referendum so that we in this country can decide who governs us."