The ballot takes place on Monday evening, after at least 15% of his own Members of Parliament submitted letters calling for a vote of confidence in his leadership.
British Prime Minister Boris Johnson will face a vote of confidence from his own party later today, which could see him removed from office.
Party official Sir Graham Brady says on Monday morning that he had received enough letters from lawmakers demanding a vote on Johnson’s leadership to trigger one.
That happened when 54 Tory lawmakers wrote to Brady.
If Johnson loses the vote among the 359 Conservative lawmakers, he will be replaced as Conservative leader and prime minister. If he wins, he will likely be safe from another challenge for a year.
"The threshold of 15% of the parliamentary party seeking a vote of confidence in the prime minister has been passed," Brady told reporters outside the Houses of Parliament on Monday morning.
The vote will take place on Monday night between 6pm and 8pm UK time with a result expected to be announced shortly afterwards.
Brady indicated that a number of MPs had submitted their letters calling for a vote before the weekend's Platinum Jubilee celebrations for Queen Elizabeth, but had 'post-dated' them until after the events were over in order not to overshadow jubilee events.
Boris Johnson was informed on Sunday that the threshold had been reached to call for a vote, but Brady wouldn't be drawn on exactly how many of those 359 Conservative MPs had submitted letters to the powerful 1922 Committee that he chairs, nor how Johnson reacted when he was told about the confidence vote.
What happens if Boris Johnson wins or loses the vote?
Boris Johnson has faced a slew of ethics scandals in recent months, most notably over rule-breaking parties which were held in government buildings during COVID lockdowns.
He made history by being the first sitting prime minister found to have broken the law, when he was fined by police for attending a party during lockdown.
If Boris Johnson wins Monday night's confidence vote, he is likely to be safe for a full 12 months from any further attempts to unseat him as prime minister under current Conservative Party rules.
"Technically it's possible for the rules to be changed, but the rule at present is that there would be a period of grace," before disgruntled MPs could launch another challenge to Johnson's leadership, Sir Graham confirmed.
"A confidence vote will obviously provide a clear answer."
If Johnson loses on Monday night it will trigger a race to be the new leader of the Conservative Party, and the new British prime minister.
Some of the most prominent members of Johnson's party who could run for the top job include finance minister Rishi Sunak; foreign minister Liz Truss, and former foreign minister Jeremy Hunt who was beaten by Johnson in the last party leadership race when Theresa May was ousted as PM in 2019.
Who is supporting Johnson, and what do his critics say?
Some of Boris Johnson's supporters and critics have taken to social media to voice their opinions.
MP Jesse Norman posted copies of a letter he sent to Johnson saying that although he had been a long-term supporter of the PM, Johnson had "presided over a culture of casual law breaking at 10 Downing Street in relation to Covid."
"To describe your self as "vindicated" by the report is grotesque," Norman wrote.
However supporters like Culture Secretary Nadine Dorries launded Johnson's achievements, saying he had won an 80 seat majority at the last general election in December 2019, successfully navigated the COVID pandemic and been the "first leader to assist Ukraine" (sic).