Image copyright Various Image caption The group of eurosceptics includes (from left) Conservative Owen Paterson, Labour's Kate Hoey and Douglas Carswell of UKIP

Seven eurosceptic MPs from three parties have formed a group to act as a precursor to the Out campaign in the referendum on leaving the EU.

The "exploratory committee for the EU referendum" includes former Tory cabinet minister Owen Paterson and UKIP's only MP, Douglas Carswell.

The MPs say the group aims to "provide resources for crucial thinking".

Meanwhile, former home secretary Alan Johnson is to head up Labour's campaign to stay in the European Union.

David Cameron has said he wants a "better deal" for the UK in Europe ahead of an in/out referendum by the end of 2017.

The newly-formed exploratory committee for the EU referendum also includes Conservatives Steve Baker and Bernard Jenkin, as well as longstanding Labour eurosceptics Kate Hoey, Kelvin Hopkins and Graham Stringer.

The committee says it is "urgently" seeking to "promote co-operation amongst those who might contribute to an Out campaign".

The BBC's political correspondent Robin Brant said that while this was not the launch of the official No campaign, the move effectively heralds the start of the fight to get the UK out of the European Union.

The committee's members, he added, have been meeting since the election and have now gone public. Donors and professional campaigners are being approached.

EU referendum in focus

Image copyright Getty Images

David Cameron is starting renegotiation of the terms of Britain's EU membership ahead of a referendum. Here is some further reading on what it all means:

Q&A: The UK's planned EU referendum

UK and the EU: Better off out or in?

What Britain wants from Europe

Timeline: EU referendum debate

David Cameron has said his negotiations to reform the UK's relationship with the EU are getting "a good response" ahead of next week's European Council summit, where the issue will be formally discussed for the first time.

He has spent the past three weeks travelling around Europe, setting out his broad aims and sounding out potential allies.

The MPs' statement claims: "The prime minister... described the renegotiation in his Commons statement of 23 March as 'an opportunity to reform the EU and fundamentally change Britain's relationship with it'.

"However, there is little if any indication that the government is even asking for significant reform or fundamental change."

The statement also says legal issues arising from the Referendum Bill and "how an Out campaign might best be formed and run to inform the public about the issues" also require "urgent attention".

MPs have expressed concerns about a number of issues, including fair funding for both sides, the length of the campaign, the role of the European Union in it and the application of purdah rules limiting government announcements in the run-up to the vote.

'Catastrophe'

As the various campaigns springing up around the referendum begin to take shape, Mr Johnson said it would be "catastrophic" for the UK to leave the EU.

The former home secretary told the BBC he would not rule out sharing a platform with David Cameron if, as expected, the prime minister backs the official Yes campaign but he believed the prime minister was taking the wrong approach to his negotiations.

Image copyright PA Image caption Alan Johnson is to lead Labour's campaign to stay in the EU

"I think that's very unlikely given the way the prime minister has dealt with this," he told Radio 4's World at One.

"I was a trade union negotiator for many years and I always found the worst way to negotiate is to throw yourself on the mercy of the employer, in this case the other 27 countries, saying 'oh, please give us this otherwise we might have to leave'.

"You have got to have strong arguments and the best way to negotiate in Europe is by taking a leading role, building alliances, bringing people with you.

"There's only one person who wants us to stay in Europe more than I do and that's the prime minister. He's got himself in these machinations for party political reasons."