Britain's EU referendum debate has sparked bitter infighting in the governing Conservative Party, with Prime Minister David Cameron accusing "leave" campaigners of peddling "fantasy politics."

Cameron is appearing alongside politicians from rival parties Monday to urge a "remain" vote in the June 23 referendum on whether Britain should stay in the 28-nation European Union — and is accusing "leave" members of his own government of gambling with the country's future.

Several senior Conservatives, including Justice Secretary Michael Gove and former London Mayor Boris Johnson, back the "leave" campaign. Cameron accuses them of playing "an economic con-trick on the British people."

Former Conservative Prime Minister John Major has accused the "leave" side of running a "fundamentally dishonest" campaign but one anti-EU Conservative lawmaker says that's the "bitter ramblings of a vengeful man."