Scotland Yard said last month that 50 referrals had been made to the criminal records office for fixed penalty notice (FPN) fines over parties in Downing Street and Whitehall.
In an update on Thursday, the force said its Operation Hillman team had now recommended 100 fines, while the investigation into a dozen events remains ongoing.
It is understood that Boris Johnson has not been handed another fine, after he was punished last month over his rule-breaking birthday party in June 2020.
The Liberal Democrats said news that fines had topped 100 showed the “shocking scale” of rule-breaking in government. “Boris Johnson stood up in parliament and said Covid rules were followed in No 10 at all times,” said eader Sir Ed Davey.
He added: “Now 100 fines have been issued by the police over Partygate – it shows the shocking scale of the law-breaking in Johnson’s Downing Street and the extent of his lies.”
Police are believed to have issuing fines to Downing Street staff over a Christmas party held at No 10 on 18 December 2020 in recent days.
The festive bash – held while London was in strict Tier 3 measures – was said to have been attended by dozens of the prime minister’s staff.
Mr Johnson was forced to address the issue of the December 2020 bash after the explosive leak of a video showing staff holding a mock press conference and making jokes about a Christmas party.
It led to the resignation of government aide Allegra Stratton and the eventual announcement of an investigation by top civil servant Sue Gray’s investigation.
Scotland Yard would not confirm if fines had yet been issued over the Christmas gathering, or any other particular party, but the 18 December 2020 event is one of 12 that Operation Hillman detectives are investigating.
Mr Johnson previously said it “did not occur” to him the gathering to mark his 56th birthday was a violation of his Covid rules – but that he “now humbly accepts” he did breach the laws.