David Cameron has told Eurosceptic ministers they will be forced to quit if they want to campaign for the UK to leave the European Union.

Speaking at the G7 summit in Bavaria, the British Prime Minister said the Government would not be "neutral" during the in-out referendum campaign.

"We have a clear view: renegotiate, get a deal that's in Britain's interest and then recommend Britain stays in it," he said.

And in a warning shot to Tory MPs, Mr Cameron added: "If you want to be part of the Government, you have to take the view that we are engaged in an exercise of renegotiation to have a referendum that will lead to a successful outcome.

"Everyone in government has signed up to the programme set out in the Conservative manifesto."

Mr Cameron also made a strong hint that the in-out referendum could be held on 5 May 2016 – when elections to local authorities, the Scottish Parliament and the Welsh Assembly will be held.

Stating he was "open-minded" to holding the EU vote on the same day as other polls, the Prime Minister added: "The British public are quite capable of going to a polling booth and making two important decisions rather than just one."

The Electoral Commission has previously advised that the in-out referendum should not clash with local elections.

Mr Cameron's strongest words on the topic of his own potential rebels came the day before his EU Referendum Bill is debated in the Commons for the first time.

Obama

Mr Cameron is in Germany at a summit of world leaders, where Number 10 had suggested that Britain's renegotiation of its relationship with the EU was not on the agenda.

But concerns about the UK's exit from the union were nonetheless mentioned by Barack Obama, prior to his talks with Mr Cameron.

The President said the US-UK relationship remains strong, adding: "We have no closer partner around the world."

He told reporters: "I would note that one of the great values of having the United Kingdom in the European Union is its leadership and strength on a whole host of global challenges.

"So we very much are looking forward to the United Kingdom staying part of the European Union because we think its influence is positive not just for Europe, but also for the world."

Mr Cameron, who recently embarked on a tour of Europe to seek support in his bid to renegotiate Britain's relationship with Brussels, has said he is "shooting for" any reforms to be "legally binding". This suggests something short of full EU treaty change by 2017.

The Prime Minister also dismissed the concerns of some backbenchers that the EU Referendum Bill allows the Government to take sides during the traditional pre-poll period of "purdah".

He will spend another day with world leaders in Germany before restarting initial renegotiation talks at an EU summit later this week.

Although he hopes to start the talks in earnest at a summit at the end of the month, the agenda is already packed with Russia, Greece and the Eurozone.