The Prime Minister is seen raising a glass at a leaving party in four photos from November 13 2020, with bottle of alcohol and party food around him.
Obtained by ITV News, the images come from a gathering of Downing Street’s then Director of Communications Lee Cain leaving do.
They show eight people standing closeley together, as a well as a photographer, with more people said to be present but not pictured.
Scottish Conservative Leader Douglas Ross said: “These images will rightly make people across the country very angry.
“The Prime Minister must outline why he believes this behaviour was acceptable. To most, these pictures seem unjustifiable and wrong.”
Angela Rayner MP, Labour's Deputy Leader, said: “While the British public were making huge sacrifices, Boris Johnson was breaking the law.
“Boris Johnson said repeatedly that he knew nothing about law-breaking – there’s no doubt now, he lied. Boris Johnson made the rules, and then broke them.
“The Prime Minister has demeaned his office. The British people deserve better. While Labour has a plan for tackling the cost-of-living crisis, Tory MPs are too busy defending the indefensible actions of Boris Johnson.”
SNP Westminster Leader Ian Blackford MP said: "These pictures clearly show, as the police investigation concluded, that parties did indeed take place at Downing Street during lockdown, and that the Prime Minister was there. It is sickening.
"Boris Johnson told us firstly that no parties took place during lockdown, then he said he wasn't at them and that he was angry about them. He is a serial liar and cannot be allowed to get away with it.
"It is truly a disgrace that Tory MPs are keeping him in Downing Street – he demeans the office that he holds. It is time for them to do the decent thing, for once, and get rid of him. This charlatan should be an ex-Prime Minister by now."
Liberal Democrat deputy leader Daisy Cooper said the images show Mr Johnson “has taken the British people for fools” as she called for Tories to remove him from office.
“It’s becoming clearer than ever that Boris Johnson lied to the British people and to Parliament,” she said.
“Conservative MPs must do their duty and sack this law-breaking Prime Minister. Every day he remains in office will do more damage to public trust and to our democracy.”
At the time the photographs were taken, England had been put back into strict lockdown with parties outside of your household banned.
Six wine bottles are on the table, one is clearly half empty.
ITV described Mr Johnson as holding half a glass of fizz in the images, while a ministerial red box is perched on a chair in front of him.
The Prime Minister only received one fine during the Met’s investigation, for the gathering for his 56th birthday in June 2020.
Scotland Yard did issue a fine to at least one individual who attended a gathering on the date of Mr Cain’s leaving do, but the force declined to say what the offending event was.
The images cast fresh doubt on the Prime Minister’s claims that he was unaware of rule-breaking in Downing Street.
On 1st December 2021, he told MPs “all guidance was followed completely in No 10.”
And on December 8, he again told MPs: “I have been repeatedly assured since these allegations emerged that there was no party and that no Covid rules were broken”.
That same day he told a Downing Street press conference “all the evidence I can see is that people in this building have stayed within the rules.”
Parliament’s Privileges Committee is due to begin an investigation into whether he knowingly misled MPs by denying any knowledge of the parties.
Doing so would mean the Prime Minister had broken the ministerial code and normally be considered a resigning matter.
It comes with Sue Gray’s report set to be published in the coming days.
Downing Street declined to defend the scene portrayed, saying the Prime Minister will comment after the Sue Gray report into partygate is published in the coming days.
A No 10 spokesperson said: “The Cabinet Office and the Met Police have had access to all information relevant to their investigations, including photographs.
"The Met have concluded their investigation and Sue Gray will publish her report in the coming days, at which point the Prime Minister will address Parliament in full.”
It comes just hours after Downing Street admitted organising a meeting with Ms Gray to discuss the report.