Brexit jitters pushed the pound down as sterling volatility surged to levels not seen since the financial crisis yesterday after three EU referendum polls put the leave campaign in the lead.

David Cameron, the prime minister, warned on Monday of a "decade of uncertainty" if Britain votes to leave the EU, while Boris Johnson, the former London Mayor, said it was a "delusion" to believe that "bartering away our freedom and democracy" would boost UK prosperity.

As the rival camps clashed on the economy, the price of insuring against a collapse in the pound against the dollar jumped to its highest since the start of 2009 after a poll showed 45pc of Britons would vote to leave the EU in the June 23 vote.

One-month implied volatility climbed to 22pc after YouGov's online poll of almost 3,500 people showed just 41pc would vote to stay in.