Battle lines drawn for EU referendum after Prime Minister David Cameron warns leaving would be "leap in the dark"

After striking a new deal with other EU leaders in Brussels late on Friday night, the Prime Minister and Witney MP said the promised in/out vote would take place on June 23.

But he faced a brusing weekend as it emerged Mayor of London Boris Johnson and Michael Gove, Justice Secretary and one of Mr Cameron's closest political allies, would be backing the Vote Leave campaign.

The Prime Minister has said ministers are free to campaign on either side, with six members of the cabinet and up to half his parliamentary party now backing so-called 'Brexit'. 

Meanwhile in Oxfordshire, Banbury MP Victoria Prentis, Oxford West and Abingdon MP Nicola Blackwood, Wantage MP Ed Vaizey, also a minister, and Henley MP John Howell, have backed the 'in' campaign.

Oxford East MP Andrew Smith has yet to declare his allegiance publicly.

This weekend Oxford University vice-chancellor Louise Richardson backed the campaign to remain in the European Union.

Now Oxford Brookes University has followed suit. Speaking after the referendum date was announced, Vice-Chancellor Professor Alistair Fitt said:  “As an institution which benefits greatly from membership of the EU, Oxford Brookes will be supporting the Universities for Europe campaign for remaining as a member of the EU.”      

“Aside from the wider advantages to society, business and the country as a whole, the EU is vital to higher education."

In Oxford, Labour city councillor John Tanner claimed Mr Cameron's "pantomime in Brussels changes very little" but Britain "belongs in the European Union", echoing comments made by his party leader Jeremy Corbyn over the weekend.

He warned leaving the EU could damage car production and scientific research in Oxford. 

Mr Cameron said leaving would threaten Britain's "economic and national security".

He said: "Those who want to leave Europe cannot tell you if British businesses would be able to access Europe's free trade single market, or if working people's jobs are safe, or how much prices would rise. All they're offering is a risk at a time of uncertainty - a leap in the dark," he said.

Among the first ministers to declare they would be campaigning for an "in" vote were Home Secretary Theresa May, Business Secretary Sajid Javid, International Development Secretary Justine Greening and Transport Secretary Patrick McLoughlin.

Culture Minister and Wantage MP Ed Vaizey said: "I am pleased with what the Prime Minister has achieved with negotiations and remain convinced Britain should stay in the European Union.

"I represent a constituency of huge science and technology businesses which attract skills from all over Europe and attracts investment.

"We are a powerful nation and could survive outside the European Union but I think the experience of my constituency show we are better off in the European Union because of the benefits: attracting foreign investment and EU investments.

"It would be much harder to thrive otherwise and I think young people in my constituency also see the great opportunity being in the European Union offers them."

Oxford West and Abingdon MP Nicola Blackwood wrote on Twitter: "#EURef defining choice for our generation.

"I back IN for jobs & security but I'll fight with @reformineurope for a responsive reforming EU."

She added: "UK is a science powerhouse. Voting IN protects life saving research, key R&D jobs &science & tech start ups."

Banbury MP Victoria Prentis tweeted: "The PM's deal means Britain is stronger in Europe. Being in means more jobs, lowers prices & greater influence in the world.

"This is a good deal for our economy – less red tape, less regulation and more jobs in the UK from the EU’s single market."

Henley MP John Howell said: “I am delighted that we now have a date for the referendum on whether or not we should remain in the EU, as it is absolutely right that the people should have their voice heard. 

"My personal opinion is that the UK is far stronger as part of the EU and that it is from within the EU that we can have the greatest influence on the world stage.  I will therefore be voting to say in. I will be campaigning to ensure people have an objective list of facts before making their decision.”

Mr Tanner said: "Quitting the rest of Europe will damage Oxford’s car factory, science research at Culham and much more.

"Half Britain’s exports go to the rest of the EU. Outside Europe, Britain would have no say over EU trade rules.

"Parental leave, minimum holidays, equal treatment for casual workers, are all thanks to the European Union. Britain cannot tackle migration, terrorism or climate change on its own.

"A vote to Leave would be bad for Oxfordshire, bad for Britain and what’s more bad for Europe."