Mortgages are set to rocket by nearly £1,000 a year if Britain quits the European Union, David Cameron has warned.
Short-term uncertainty caused by a vote in favour of leaving the 28-member block would tighter credit conditions and fuel a rise in interest rates, according to Treasury analysis.
But the Leave campaign claimed that voters "cannot trust" Government on the EU.
In a robust letter to the Prime Minister and Chancellor, Boris Johnson and Michael Gove warned that remaining leaves the country "dangerously and permanently exposed to being forced to hand over more money and accept damaging new laws".
Remain campaigners dismissed the letter as "reckless nonsense" and accused the Brexit camp of "misleading" the public.
Stronger In said the average new mortgage will cost £920 a year while first time buyers, who generally have lower value loans, face paying £810 more annually.
"Nearly all experts agree there will instant shocks to the economy if we leave the EU and there is a clear and present danger of higher mortgage rates," the Prime Minister told The Mail On Sunday.
Combined with predicted higher unemployment and lower wages following a Brexit, the hike in mortgages would make it much tougher for first time buyers to get onto the housing ladder, they warned.
But Mr Johnson, the Justice Secretary and Labour's Gisela Stuart branded Treasury analysis previously released by the government predicting Brexit would hit households by more than £4,000 as "indefensible" and "bogus".
Setting out detailed claims about the "dangers" of the EU, they criticised the Prime Minister's renegotiation package for failing to secure real change.
Britain will be forced to bow to the will of eurozone nations if it remains in the bloc and will be pushed into funding future bailouts for ailing members states, they warned.
"If we stay, we are tying ourselves to a broken Eurozone economy while simultaneously accepting unlimited migration of people trying to escape that broken economy," they wrote.
"British taxpayers are already paying nearly £2 billion for Albania, Macedonia, Montenegro, Serbia and Turkey to join the EU. The European Commission recently announced an acceleration of these plans and is already extending visa-free travel to the border with Syria and Iraq. This is dangerous. The Government's claim that Britain has a veto is meaningless if it is simultaneously trying to 'accelerate' this process."
Jayne-Anne Gadhia, chief executive of Virgin Money, said: "Even if the base rate stays flat after a vote to leave the EU, mortgage prices could rise considerably - leading to more expensive monthly mortgage payments for everyone."
A Britain Stronger In Europe spokesman said: "As any credible expert will tell you, this letter from Leave is reckless nonsense - they are now guilty of actively misleading the British people.
"The Leave campaign cannot produce a single expert who believes there is any prospect of Turkey joining the EU. The UK retains a full veto over any new member.
"We have clear guarantees we will not contribute to bail outs and protections against Eurozone integration."
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