Public services such as health and education could face £36 billion of cuts if the country votes to leave the European Union, George Osborne has warned.
The Chancellor warned the price of Brexit would be paid by British families, who would be £4,300 a year worse off according to Treasury analysis.
As well as that long-term impact, he warned that in the short term the country would face a "profound economic shock and real instability".
Britain's economy would shrink by 6 per cent by 2030 if the country replicated Canada's trading agreement with the EU, as advocated by Boris Johnson, according to the Chancellor.
Mr Osborne said: "Under any alternative, we'd trade less, do less business and receive less investment.
"And the price would be paid by British families. Wages would be lower and prices would be higher.
"The most likely result is that Britain would be poorer by £4,300 per household. That is £4,300 worse off every year, a bill paid year after year by the working people of Britain."
He said the analysis produced by the Treasury was "serious and sober" and showed "British families will pay a heavy economic price if we leave the EU."
Mr Osborne rejected the claims of Leave campaigners that the country would benefit from the savings made by not contributing to Brussels' coffers.
Speaking in Bristol he said: "Don't believe the flimsy claim that at least we would get some money back by not paying our 1p on every £1 we raise in taxes to the European budget.
"We'd lose tens of billions of pounds in money for our public services, because our economy would be smaller and our families poorer.
"The most likely bill our public services would pay for leaving the EU is £36 billion.
"That's the equivalent of 8p on the basic rate of income tax."
