Mayor of London Boris Johnson has formally announced he is to campaign for a British exit from the European Union in the referendum.
He confirmed his intentions in a statement to media outside his home in north London.
Mr Johnson said David Cameron's renegotiation had failed to deliver fundamental change in Britain's relationship with Brussels and said the EU was is "in real danger of getting out of proper democratic control."
He insisted that he had agonised over the decision before finally declaring his hand.
"The last thing I wanted was to go against David Cameron or the Government but after a great deal of heartache I don't think there is anything else I can do.
"I will be advocating vote leave ... because I want a better deal for the people of this country to save them money and to take back control," he added.
David Cameron has warned that Britain has "100 days to secure our future", as a poll suggests the final result hangs in the balance.
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