UK Prime Minister Boris Johnson faces another assault on his leadership today, after fresh allegations he "waved' away his adviser's concerns that a garden party he attended would be seen as a contravention of lockdown rules.

Johnson has "categorically" denied he was warned the drinks event in the garden of his official 10 Downing Street residence during lockdown in May 2020 would break the rules.

But his former chief political adviser Dominic Cummings said the prime minister "lied to parliament" over the gathering. Cummings says he personally warned Johnson about the drinks but he "waved away" concerns.

The PM will attempt to win over his fellow Conservative lawmakers at Prime Minister's Questions this lunchtime while his future hangs in the balance as he awaits the investigation by the senior civil servant Sue Gray into the so-called "Partygate" scandals.

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These latest accusations by Cummings that Johnson lied to parliament could prove the most damaging, if they are to be believed. This is about whether the PM thought a drinks event in his garden was a work meeting or a social gathering, which was banned at the time.

It was clearly a party following a leaked email from Johnson's Private Secretary Martin Reynolds, who invited around 100 people to "make the most of the lovely weather" and bring their own "booze" for socially distanced drinks in the garden. Thirty to 40 people attended, including Johnson, who admitted he had spent 25 minutes at the event to thank everyone for their hard work but implicitly thought it was a work meeting. He apologized to parliament and said that in hindsight, he should have closed it down.

Now Cummings, who came close to being sacked for breaking lockdown rules, has said he will swear under oath that he had warned the PM about the party but Johnson dismissed his concerns. The political strategist is a highly controversial figure, accused of lying about his reasons for breaking COVID-19 rules to drive his family to the north of England where he was pictured at a tourist site during lockdown.

Initially the PM refused to sack him over this, though he was dismissed later in the year. Cummings left disgruntled and has since become one of Johnson's fiercest critics, responsible, it is thought, for many of the "Partygate" leaks.

Johnson hit back on Tuesday, categorically denying Cummings' accusations, saying no-one warned him the drinks event was against the rules.

There are reports, though, that at least two other people who were there back up the allegations.

Several members of the cabinet, including Deputy Prime Minister Dominic Raab, have come out in support of the PM. While one of the leading contenders to replace Johnson should he resign, Chancellor Rishi Sunak, walked out of a TV interview after being repeatedly asked if Johnson should resign if he lied.

All now rests on the findings of Sue Gray's investigation, which could be reported as early as the end of this week. If she finds Johnson lied and knew these were parties, then he will face intense pressure to resign.

If it's a more nuanced report, then his closest allies hope that will be enough for him to continue in the post. Over the weekend, Conservative members of parliament returned to their constituencies to judge the mood among their supporters. One came back saying that 60 to one thought the PM should step down.

Only a handful of lawmakers have openly called for Johnson to resign, but if 54 Conservative MPs write a letter of no confidence in Johnson, that will trigger a leadership contest.