British families will be £4,300 worse off a year if the country leaves the EU, Chancellor George Osborne has said.
Writing in The Times, Mr Osborne attempted to bolster the government's case to remain in the Union, warning a vote to leave would permanently hit British households in the pocket.
He wrote: "Put simply: over many years, are you better off or worse off if we leave the EU?
"The answer is: Britain would be worse off, permanently so, and to the tune of £4,300 a year for every household."
The Chancellor's comments come ahead of a weighty government report on the cost of leaving the EU, due out later today.
Read ITV News Deputy Political Editor on the planned Treasury report
According to Mr Osborne: "The Treasury analysis shows that under all plausible alternatives to British membership of the EU we would have a less open and interconnected economy - not just with Europe but, crucially, with the rest of the world.
He said the report has modeled the scenarios for life outside the EU, looking at Norway's relationship with Brussels, Canada's bilateral agreement and a deal under World Trade Organisation rules.
If the UK replicated Canada's agreement - as advocated by Boris Johnson, the Leave campaign's highest profile campaigner - the Treasury predicts the economy would shrink by 6% by 2030.
Vote Leave dismissed the report as further scaremongering by the government.
John Redwood, the former cabinet minister, said the government had a poor track record when it came to the EU, and referred to the attempts to keep the UK in the EU Exchange Rate Mechanism (ERM) in the 1990s.
"The ERM destroyed jobs and caused misery for families across the country," Mr Redwood said.
"The remainers were wrong then, and they are wrong now - people should not trust their judgement on the EU."
Mr Johnson, meanwhile, used his Daily Telegraph column, to complain that: "All the usual suspects are out there, trying to confuse the British public and to persuade them that they must accept the accelerating loss of democratic self-government as the price of economic prosperity."