Media playback is unsupported on your device Media caption The prime minister is to make a long-awaited speech on Europe in January

Britain is "perfectly entitled" to ask for a change in its relationship with Europe, Prime Minister David Cameron has said.

Speaking on the BBC's Andrew Marr Show, he said voters would be offered "real choice" on this at the next election.

But he said being entirely outside the EU would not be "right for Britain".

Mr Cameron is due to make a long-awaited speech on Europe later this month. Many Tory MPs are urging a referendum.

The prime minister said any vote would happen within five years.

Currency considerations

"People should be in no doubt that the Conservatives will be offering at the next election a real choice and a real way of giving consent to that choice," he said.

"What's happening in Europe right now is massive change being driven by the existence of the euro.

Should we look at the arguments about should it be harder for people to come and live in Britain and claim benefits... frankly we should David Cameron

"The countries of the euro, they've got to change to make their currency work - the need to integrate more, they need to make changes to all their systems more."

He continued: "What that means is they are changing the nature of the organisation to which we belong.

"And so we are perfectly entitled, and not just entitled but actually enabled because they need changes to ask for changes ourselves."

As part of a series of EU reforms partially aimed at protecting the euro, the European Central Bank will be directly supervising around 200 of the largest European banks from 2014 - but will have the right to intervene if smaller lenders are in trouble.

With regards to the repatriation of some powers back to Britain, Mr Cameron said the government was already reviewing this.

"As you [EU members] need to make your changes, there are changes that Britain would like to make too."

He said people had said it was never possible to make changes to Britain's relationship with Europe, but he has already done this.

Immigration control

Mr Cameron was asked if the free movement of people inside Europe could be limited in order to give Britain more control of its borders and as part of a renegotiated relationship.

The real fight over Britain has not yet been joined. Europe is waiting to see what David Cameron will say in his 'big speech' later this month

The prime minister said a key reason to be a European Union member were freedoms, such as the movement of services, goods and people and there were already restrictions in place.

"Should we look at the arguments about should it be harder for people to come and live in Britain and claim benefits... frankly we should."

Mr Cameron also highlighted fishing quotas as an area of concern.

He also said he did not think it would be "right for Britain" - or in the "national interest" - to leave the EU entirely, pointing out some 50% of nation's trade was with the EU.

The UK would have "no say over the rules of the market into which we sell" if it left, he added.

In the wide-ranging interview, Mr Cameron made a number of points, including:

He said he was "absolutely determined" to overhaul the deportation system so the radical cleric Abu Qatada and others could be deported from the UK before they appeal

The prime minister also said he was "absolutely clear" Britain would defend the Falkland Islands in the face of mounting pressure from Argentina

He also confirmed he wanted to remain prime minister until 2020

When asked by Andrew Marr if a decision over Europe would have to wait "five years or possibly 10" while negotiations with the EU were completed, Mr Cameron replied: "No, no, that's not going to happen."

'Pretty odd people'

During the interview, Mr Cameron was also asked about his previous description of UK Independence Party members as "fruitcakes, loonies and closet racists".

He said there were "some pretty odd people" in the party.

Ukip's leader Nigel Farage later told Sky News the prime minister's comments revealed "how disconnected he is".

He added there was little prospect of any deal with the Conservative Party "while that man leads it," but conceded he 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".