Police are contacting partygate 'suspects' after being handed a dossier of evidence by Sue Gray.
Scotland Yard said people accused of breaking Covid rules at parties held in Number 10 and across Whitehall, would have to provide a "reasonable excuse" or face a fine.
Commander Catherine Roper, who leads the Met’s Central Specialist Crime Command, said: "If the decision is to take enforcement action then a report will be sent to the ACRO Criminal Records Office which will issue the fixed penalty notice.
"Recipients can pay the fixed penalty and the matter will be considered closed."
Meanwhile, Scotland Yard faced criticism from a former Attorney General over their response to the scandal.
Lord Morris of Aberavon was speaking after Scotland Yard constrained the Sue Gray inquiry report into "partygate" over concerns that its contents may impact the police investigation into possible lockdown breaches.
Lord Morris said: "I am dismayed with the vacillation of the Metropolitan Police.
"Surely it is in the public interest that major concerns over events in Downing Street be investigated and reported on.
"Any prejudice that might result in fines would be a disproportionate concern."
The Metropolitan Police have asked Ms Gray, a senior civil servant, to make only "minimal reference" to No 10 events which are subject to a criminal investigation, buying more time for Prime minister Boris Johnson as he faces a threat to his leadership.
Earlier this week Metropolitan Police Commissioner Dame Cressida Dick confirmed that officers were investigating "potential breaches of Covid-19 regulations" at events held at Downing Street and in Whitehall in 2020.
Lord Morris added: "Could I ask whether the commissioner consulted with the CPS (Crown Prosecution Service), who in turn - as it did in my day - at least keep the AG (attorney general) informed in any such event involving public figures?
"The AG supervises the CPS. Did she have a role in this?"
In a statement on Friday, Scotland Yard said: "For the events the Met is investigating, we asked for minimal reference to be made in the Cabinet Office report.
"The Met did not ask for any limitations on other events in the report, or for the report to be delayed, but we have had ongoing contact with the Cabinet Office, including on the content of the report, to avoid any prejudice to our investigation."
Rather than the statement indicating an escalation of the investigation, PA learned that officers were only looking into possible breaches of Covid rules that may warrant fixed penalty notices, with the Met's concerns centring on the ability of officers to effectively investigate.
