The global economy will suffer “a shock” if Britain votes to leave the European Union, the world’s 20 leading nations have warned. In a joint statement, finance ministers from the G20 group of major economies unanimously agreed that the risk of “Brexit” posed dangers for international stability.
 In what will be seen as a coded attack on Boris Johnson, who is campaigning to leave, he added that the leaving the EU would not be “some amusing adventure” but a serious threat to Britain and the world.

Speaking in Shanghai, the Chancellor said: “Here at the G20, finance leaders and central bank governors of the world's biggest economies have raised serious concerns about the risks posed by a UK exit from the EU.

"They have concluded unanimously today that what they call the shock of a potential UK vote to leave is among the biggest economic dangers this year. If that's their assessment of the impact on the world economy, imagine what it would do to the UK.

"This isn't some amusing adventure into the unknown. A British exit would hurt people's jobs, livelihoods and living standards - it's deadly serious," he said.

"It's my responsibility as Chancellor to make it clear to people what the economic risks are - and that we are stronger, safer and better off remaining in a reformed EU."

Reports from Shanghai suggested that Mr Osborne’s team were instrumental in ensuring that Brexit was included in the final summit communique.

The Italian Finance Minister, Pier Carlo Padoan, said that a decision by Britain to leave the EU would have negative global consequences.

"We would classify a UK exit from the EU as a powerful geopolitical shock, a negative shock," he said.