• U.K. Prime Minister Boris Johnson is facing the political battle of his career.
• Johnson could face a vote of no confidence if enough of his own lawmakers turn against him.
• Johnson has come under immense pressure amid multiple reports of parties and gatherings that were allegedly held by government staff, and some attended by Johnson, during Covid lockdowns in the U.K.

LONDON — U.K. Prime Minister Boris Johnson is facing the political battle of his career with a growing rebellion from within his own party after multiple allegations of parties and gatherings of government staff, including himself, during coronavirus lockdowns.

An inquiry is currently taking place to establish the nature and purpose of the gatherings and whether Covid legislation at the time was broken. The findings of that investigation are being eagerly awaited as the results could prompt more Conservative Party lawmakers to turn on Johnson and mount a confidence vote and leadership challenge.

CNBC has a short guide to a very British political crisis:

What's going on?

Johnson's leadership is under immense pressure after weeks of media reports of multiple parties and gatherings attended by government staff, including Johnson at times.

One gathering in particular has snared Johnson which was held in May 2020 at the height of the first lockdown, when the general public was only allowed to meet one other person from outside of their household, in an outdoor setting.

Johnson admitted to Parliament last week that he attended the party — billed as a "bring your own booze" gathering in Downing Street's garden to which around 100 people were reportedly invited. But he told lawmakers that he had only attended the party for 25 minutes in order to "thank groups of staff" for their hard work and that he "believed implicitly that this was a work event."

A former advisor and now prominent political foe, Dominic Cummings, has accused Johnson of lying to Parliament, saying that the prime minister was warned that the party contravened Covid rules at the time. Johnson has denied this.

If Johnson is found to have lied to Parliament, he would be expected to resign, politicians have said, including his deputy Dominic Raab.

For now, many lawmakers within Johnson's Conservative Party say they are awaiting the results of a probe, led by senior civil servant Sue Gray, into the nature of the parties and gatherings.

Others have already declared publicly they think it's time for Johnson to go, with a growing number sending letters of no-confidence to the chairman of the influential "1922 Committee."

So what is the 1922 Committee?

Essentially, the 1922 Committee is a parliamentary group that oversees Conservative Party leadership challenges. It is an influential group in the party, formed of a number of backbench Conservative lawmakers.

Backbench lawmakers differ to "frontbench" ones (that sit next to the prime minister in Parliament) in that they do not head up government ministries or departments. The committee (or "the 22" as it's known) meets weekly when the House of Commons is sitting, and is seen as a way for backbenchers to co-ordinate and discuss their views independently of frontbenchers.

If Conservative lawmakers have no confidence in their leader they can submit letters stating this to the group's chairman, Graham Brady, asking for a vote of confidence to be held. To trigger such a vote, however, 15% of Conservative MPs (or 54 of the current 360 Tory MPs) have to write letters to Brady.

Sky News reported on Wednesday that it believed that 12 more letters were needed to trigger a leadership challenge but as the letters are handed in confidentially, only Brady knows the true number. We know the vague number of letters as some MPs have publicly stated that they have written to the 1922 Committee stating they no longer have confidence in Johnson's leadership.

Fun fact: The 1922 Committee was actually set up in April 1923 following an initiative by new Tory MPs (elected at the 1922 election) to improve cooperation within the party.

What happens next?

While some MPs are saying they are awaiting the findings of Sue Gray's report into what has been dubbed "partygate" by the British press, if the 1922 Committee chairman does receive enough letters of no confidence then a vote would be triggered.

If a majority of Tory MPs voted to support Johnson in a vote, no new vote can be called for another 12 months, according to the current rules, although Sky News reported that the 1922 Committee is considering whether to change that rule to allow for two votes per year.

If Johnson lost the vote, he would be forced to step down and a Conservative leadership contest would begin. In that eventuality, Johnson, as an ousted leader, would not be allowed to stand.

Of course, another alternative would be for Johnson to resign of his own accord but he shows no signs of intending to do so with Sky News reporting that Johnson appears ready to come out fighting against his enemies, reportedly telling allies to "bring it on."

So what happens next could largely depend on how MPs, who are still undecided on Johnson's leadership, respond to the findings of Sue Gray's inquiry now expected to be released next week.

Johnson could possibly hold on until local elections in May, however, if lawmakers decide to let the polls act as a gauge of public opinion on the party. Some might not want to take that risk with a YouGov/Times newspaper voter poll out last week already pointing to a drop in support for the Conservatives and giving Labour the lead.

What do Johnson's critics say?

Unsurprisingly, the opposition Labour Party has been scathing about Johnson's leadership and his comments on his attendance at the May 2020 party, calling on the prime minister to resign.

When Johnson offered his "heartfelt apologies" to the nation about attending the event, Labour leader Keir Starmer said Johnson's explanation for his attendance (that he believed it was a work event) was "so ridiculous that it's actually offensive to the British public" as he called on Johnson "to do the decent thing and resign."

Last Sunday, Starmer accused Johnson of lying about what he called "industrial scale partying" in Downing Street.

"The facts speak for themselves, and the country has made up its mind," he said, adding it was "blindingly obvious what's happened ... I think he broke the law, I think he's as good as admitted that he broke the law," he told the BBC.

Angela Rayner, deputy Labour leader, told CNBC Wednesday that Johnson is "starting to look really silly now and the British public are very angry about it."

"There's one thing breaking the rules that you set, but there's quite another one [when] you're trying to lie your way out of it and deceive people and make them feel like they're somehow silly for following the rules ... It's not going down well, at all, across all parts of the United Kingdom," Rayner told CNBC's Rosanna Lockwood.

She believed that the threshold for a vote of confidence in Johnson was close to being reached, saying such a vote was a "real possibility" now.

Johnson has been heavily criticized within his own party too. At Prime Minister's Questions in Parliament on Wednesday, which started in dramatic fashion with one Tory MP crossing the parliament floor to defect to Labour, senior Tory MP David Davis told Johnson: "In the name of God, go!"