Officers were called to a property in Green Street, near Marble Arch Tube station, at 1.30am on Sunday morning, where they found 50 people attending an illegal party.
The organiser of the event, a 29-year-old man, was put forward for a £10,000 fine for breaching lockdown rules.
A further 50 fixed penalty notices of £800 each were given to the man’s guests.
Shortly after arriving at the property in Green Street, police were called to another illegal gathering in nearby Brooks Mews at 2am.
Officers found 20 people at the property and all attendees were issued with £800 fines.
Inspector Kevin Fagan of the Central West Command Unit, which covers Westminster, said: “Despite recent announcements about how and when Covid restrictions may be eased, nothing has changed in terms of the regulations.
“Illegal gatherings like this are irresponsible and put pressure on the emergency services who have do deal with the consequences of these people’s selfish actions.
“The rules are clear, as should be the message that the police will enforce them where wilful breaches are found to have taken place”.
It comes as two men will face trial this summer for allegedly organising a rave in November in breach of coronavirus restrictions.
Robert Bagot and Henok Yefru, both 32, are accused of helping to organise the event in Deptford, south London, on November 22 last year.
Both Mr Bagot and Mr Yefru accept being present but deny organising the gathering.
The pair both denied a single count of holding or being involved in holding a rave-type gathering in England of more than 30 people indoors - an offence with a maximum fine of £10,000.
City of London Magistrates’ Court heard that one of the issues in the case will be whether lending sound equipment to the rave would meet the definition of being organisers of the event.
Their trial was listed for a day-long hearing at Westminster Magistrates’ Court on July 19.