Rory Stewart has been knocked out of the race to become Britain's next prime minister, leaving four candidates led by former foreign secretary Boris Johnson.

International Development Secretary Mr Stewart received the fewest votes in the third ballot of Conservative MPs and so drops out of the contest, while Mr Johnson extended his commanding lead among his colleagues. 

Former London mayor Mr Johnson received 143 votes, ahead of Foreign Secretary Jeremy Hunt on 54, Environment Secretary Michael Gove on 51 and Home Secretary Sajid Javid on 38.

Mr Stewart won 27 votes - 10 fewer than he received in the second ballot - and was eliminated.

Two further ballots are scheduled for tomorrow, which will whittle the four candidates down to a final two.

Rory Stewart is the latest contender to be knocked out of the Conservative leadership contest

The 160,000 grassroots party members then choose their new leader, who will take over from Theresa May as prime minister, with the result declared in the week beginning 22 July.

Mrs May officially stepped down as Conservative party leader this month over her failure to deliver Brexit on time, although she remains prime minister until her successor is chosen.

She struck an exit deal with Brussels last November, but failed three times to get it through the House of Commons.

Initially a rank outsider, Mr Stewart's social media-driven campaign had garnered momentum as the most opposed to a no-deal Brexit.

The only candidate to rule out leaving the EU with no deal, Mr Stewart had made unlikely progress to reach the last five.

He wanted to try again to get the divorce deal through parliament, but the other candidates all warn that without a change, Britain must be ready to leave with no deal at all.

Tomorrow's fourth ballot takes place between 10am and 12pm, with the result declared an hour later.

If no candidates have voluntarily withdrawn and three remain, MPs are then scheduled to vote again between 3.30pm and 5.30pm.

With today's elimination, Mr Stewart has shared the unfortunate fate of Dominic Raab who was forced out of the race following the first debate involving frontrunner Mr Johnson last night. It ended with no clear winner after a fractious debate taking in Brexit, Islamophobia and climate change.

However, Michael Gove claimed he "won the debate" on BBC Newsnight, "because I had the most detailed answers and I have a clear plan to how we can deliver Brexit and make sure we get all the benefits of life outside the European Union."

Mr Johnson came under fire for his tax plans, and was also taken to task over his comments comparing veiled Muslim women to "letterboxes" and "bank robbers".

Mr Johnson said he would lift the National Insurance threshold for the low-paid, but there should be a "debate" about the 40p higher income tax rate, which currently kicks in at £50,000.

"It does seem to be very odd that in the Conservative Party people should seriously question whether it is right to try to lift nurses and heads of maths departments and police inspectors out of the top rate of tax," he said.

But Foreign Secretary Mr Hunt said people accused the Tories of being "the party of the rich" and "we must never fall into the trap of doing tax cuts for the rich and confirming that prejudice".

Additional reporting PA