At least 50 more fines have been issued for breaching Covid regulations at Whitehall and Downing Street.
A Met Police spokesman said: "As of Thursday 12 May, Operation Hillman, the investigation into breaches of COVID-19 regulations in Whitehall and Downing Street, has made more than 100 referrals for fixed penalty notices (FPNs) to the ACRO Criminal Records Office.
"These referrals have continued to be made throughout the period since our last update on Tuesday 12 April and the investigation remains live."
The investigation is ongoing and more fines are expected to be issued.
A No.10 spokesman has refused to comment on the latest set of fines.
Prime Minister Boris Johnson gets off the plane after landing in Helsinki, Finland
Frank Augstein
Mr Johnson previously said it “did not occur” to him the gathering to mark his 56th birthday was a violation of coronavirus rules, but that he “now humbly accepts” he did breach Covid-19 laws.
He is alleged to have been at six of the 12 events being examined by the force, meaning it is possible he could be fined again.
The Met sent out more than 100 questionnaires earlier this year in relation to allegations of law-breaking parties in Government buildings while pandemic-related restrictions were in place.
It was previously reported that some Government staff had received new questionnaires from the force in relation to a leaving party for the Prime Minister’s former communications director, Lee Cain, on November 13, 2020.
But Mr Johnson indicated earlier this month that he was not among those to be sent one, telling Times Radio, “I am not commenting on this stuff generally, but the answer to that is no, not so far, or certainly not to my knowledge.
“All of this will become clear with the end of the investigation.”
There have been ongoing calls for Mr Johnson to resign over the saga from opposition MPs, as well as his own backbenches, but he has repeatedly said he is determined to get on with the job.
In addition to the Scotland Yard probe and an investigation by senior civil servant Sue Gray into the partygate claims, the PM is facing a third inquiry by the Privileges Committee into whether he misled Parliament with his repeated assurances that Covid rules were followed in No 10.
Meanwhile, Labour leader Sir Keir Starmer has pledged to stand down if he is fined for breaching coronavirus regulations, after he was filmed last year drinking beer with staff in a party office in Durham.
Asked in an interview broadcast on Thursday if he too should resign in the event Sir Keir steps down, Mr Johnson told LBC: “What matters to me and the thing that gets me out of bed in the morning is not stuff that, I think, is, however fascinating is to people, I don’t think is material to the cost of living.
“What matters to me is getting our people through the aftershocks of Covid and coming out strongly the other side, but making sure that we use … all the legislative firepower in the Queen’s Speech, all the things that we’re doing on skills, on infrastructure, on the cost of energy, on education, to make sure that we have a strong economic recovery, that we power through.”
On Wednesday, Communities Secretary Michael Gove said it was “bonkeroony” to suggest Mr Johnson should have to resign over lockdown parties in Downing Street.