But the final decision on which of them will become the UK’s second female prime minister, after Margaret Thatcher, will be made by Conservative Party members in a postal ballot due to end on September 9.

A jubilant Mrs May – the runaway front-runner – said that Britain needs “strong, proven” leadership to handle Brexit negotiations and unite the country as she spoke of her “delight” to have won so much support from her colleagues.

While Mrs May enjoys a clear advantage among Tories at Westminster, she will be acutely aware that grassroots Conservatives rejected the MPs’ choice in both previous elections conducted under the current system, opting for Iain Duncan Smith and David Cameron over Kenneth Clarke and David Davis.

Mrs Leadsom, who played a prominent role in the campaign for Britain to leave the EU, is likely to attract votes from Eurosceptic activists who want a “Brexit prime minister” to oversee withdrawal negotiations.

Although signed up to the Remain camp, Mrs May maintained a low profile during the referendum, and sought to neutralise the issue as she launched her leadership bid by making clear she would not seek to overturn the result and declaring: “Brexit is Brexit.”

The new prime minister will be chosen by an electorate of around 150,000 Conservative Party members.

The deadline for getting a vote by joining the party has already passed.

The latest stage in the bitter battle to chose Britain’s next prime minister comes as Justice Secretary Michael Gove’s team insisted he was kept in the dark about a plot to get supporters of Mrs May to switch sides in order to block the surge of Mrs Leadsom.