Prime Minister Theresa May has told Conservative MPs she won't lead the party into the next general election, according to the party's chairman.

The admission comes after a no confidence vote was triggered by at least 48 letters from Tory MPs unhappy with her Brexit strategy.

A secret ballot of all 317 Conservative MPs got under way at 6pm, with the result expected to be announced around 9pm.

May, who became Prime Minister in 2016, needs the support of at least 159 MPs to remain party leader, but victory by a narrow margin could leave her under pressure to resign.

She addressed Tory MPs at the party's 1922 Committee before the ballot began.

MPs at the meeting reported May had "said clearly it is not her intention to lead the party into the 2022 election".

Conservative party chairman Brandon Lewis confirmed the Prime Minister's remarks in an interview on Sky News.

Another MP claimed ministers had been "crying" at the meeting, while further reports suggest the Prime Minister ruled out a snap election before 2022, such as the one she called in 2017.

Under the Fixed-term Parliaments Act, general elections are held at five-year intervals unless the government is toppled or two-thirds of MPs back an early election.

Ten of Scotland's 13 Conservative MPs have stated they will back the Prime Minister in the confidence vote.

Scottish Tory leader Ruth Davidson tweeted her support for May, praising her "cojones of steel".

And speaking to STV News earlier, her interim leader Jackson Carlaw urged Tory MPs to back the PM, saying she is "the only person capable" of delivering Brexit.

If May wins the ballot, the party will be unable to challenge her premiership for another year, however, if she loses, there will be a leadership election and she will not be allowed to run.

Making a statement outside Downing Street on Wednesday, May said: "A change in leadership in the Conservative party now will put our country's future at risk and create uncertainty when we can least afford it.

"A new leader wouldn't be in place by January 21 legal deadline, so a leadership election risks handing control of Brexit negotiations to opposition MPs in parliament."

She added: "I have devoted myself unsparingly to these tasks ever since I became prime minister, and I stand ready to finish the job."

May is under pressure after scrapping plans to hold a Commons vote on the exit deal she has struck with the European Union.

A majority of MPs were expected to vote against her Brexit deal on Tuesday.