"Boris Johnson will resign as Conservative leader today -- he will continue as prime minister until the autumn," BBC political editor Chris Mason said, adding a Tory leadership race will take place this summer and the victor replace Johnson by October.

A Downing Street spokesman said the prime minister "will make a statement to the country today".

Opposition Labour leader Keir Starmer called it "good news" that Johnson was going to quit but said what was needed was "a proper change of government".

Johnson had been clinging on to power despite a wave of more than 50 government resignations.

But Thursday's departure of education minister Michelle Donelan and a plea to quit from finance minister Nadhim Zahawi, only in their jobs for two days, appeared to tip the balance.

Northern Ireland minister Brandon Lewis kicked off Thursday's frenzied events, becoming the fourth cabinet minister to resign, writing that Johnson was "past the point of no return".

The Conservative leader late on Wednesday defiantly responded to calls from his loyalists and cabinet colleagues to step down by sacking minister and former top ally Michael Gove.