Britain's Treasury chief, George Osborne, has warned that taxes will rise and spending will be cut in the event that voters choose to leave the European Union in a June 23 referendum.

Osborne says he will have to act to avert chaos and fill a budget black hole that ministers say will emerge if Britain leaves the EU.

He told the BBC on Wednesday that "no Conservative wants to raise taxes — least of all me."

Furious members of his party backing Britain's exit say they'll block any attempts to impose an emergency "punishment" budget and warned that Osborne's position would be "untenable" if he tries to push through tax increases.

Vote Leave described the "remain" camp's position as "hysterical prophecies of doom."