GETTY David Cameron hauled Boris Johnson to Downing Street this morning for talks on his EU deal

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The Mayor of London has consistently refused to rule out backing a British exit from the EU at the upcoming in/out referendum. As recently as last weekend the Tory MP declared “there is no reason to be afraid” of cutting ties with the EU, as he promised to “come off the fence with deafening eclat” once Mr Cameron returns from Brussels with an agreed deal later this week.

Mr Johnson interrupted a half-term break for a 40-minute meeting with David Cameron in Downing Street this morning, where he was said to have been shown the “granular detail” of the Prime Minister’s draft renegotiation agreement. As he left, Mr Johnson - who also spoke to the Prime Minister over the phone yesterday - told waiting reporters: “I'll be back, no deal." Sources said Mr Johnson remains “genuinely conflicted” over whether to back Brexit or remain loyal to Mr Cameron. According to the BBC, Mr Johnson’s camp also dismissed suggestions the Mayor of London was basing his decision on whether to back Brexit on what will best serve his ambitions to succeed Mr Cameron as Tory leader.

GETTY Could Employment Minister Priti Patel back Brexit?

I'll be back, no deal Boris Johnson

As well as his continuing his fight to renegotiate Britain’s EU membership, the Prime Minister is also ready to unveil plans for new domestic laws to assert the sovereignty of the UK Parliament over Brussels. The legislation is part of his bid to appease Mr Johnson, who has questioned whether it would be a "bazooka or popgun" in taking on European judges and bureaucrats. As well as the possibility of Mr Johnson backing Brexit, leading Tory MP Liam Fox has claimed “four or five” Cabinet ministers are “certain” to campaign for Britain to leave the EU at the upcoming referendum. They are expected to include Work and Pensions Secretary Iain Duncan-Smith, Northern Ireland Secretary Theresa Villiers, Culture Secretary John Whittingdale and Commons leader Chris Grayling. Employment Minister Priti Patel and Business Secretary Sajid Javid could also back Brexit, while Education Secretary Michael Gove is said to be agonising between his euroscepticism and loyalty to the Prime Minister. It emerged last night Ms Patel has told friends she will play a "leading role" in the 'Leave' campaign.