Brexit: House prices will plummet if Britain leaves, says UK Treasury

British house prices could fall by up to 18% if the country leaves the European Union (EU), the Treasury says a claim dismissed as scaremongering by campaigners for a UK exit from the bloc.

Treasury chief George Osborne said that leaving the EU would be a "profound economic shock" that would lower property values and raise mortgage rates.

Treasury analysis estimates property prices will be worth between 10 and 18% less by 2018 if Britain leaves than if it stays.

British house prices rose 9% in the year to March, and the value of property is something of a national obsession especially in London, where the average home costs 535,000 pounds ($775,000), more than 10 times the average annual household income.

Some economists think a fall in house prices would be a good thing because it would help new buyers currently priced out of the market. Others argue any benefit would be offset by a rise in mortgage rates and economic instability.

Many international banks and ratings agencies have warned that leaving the EU would destabilise the economy, and Bank of England Governor Mark Carney said earlier this month that a British exit, or 'Brexit', could tip the country into recession.

Osborne, who was attending a meeting of G-7 finance minister in Japan today, said allies, including France, Germany and the United States, agreed that "it would be bad for the British economy if we left the European Union".

But Energy minister Andrea Leadsom, who backs a "leave" vote in Britain's June 23 referendum, said today that "the greatest threat to the economy is the perilous state of the euro" currency used by 19 EU states.

"The safer option in this referendum is to take back control of the vast sums we send to Brussels every day and Vote Leave on 23 June," she said.