Boris Johnson could be in line for £10,000 in Partygate fines as police confirmed they will quiz more than 50 people over rule-busting parties.
Barrister Adam Wagner, an expert in Covid laws, said the Prime Minister could be slapped with a massive bill if Scotland Yard find regulations were broken at gatherings he attended.
The Metropolitan Police confirmed that "formal questionnaires" will be sent out in the coming days asking party-goers for "an account and explanation" of 12 events during the pandemic.
Mr Johnson is believed to have attended six events being looked at by officers, including a BYOB drinks do in the Downing Street garden, a party in his No11 flat and a birthday gathering in the Cabinet room.
The force is also reviewing its decision not to investigate a Downing Street Christmas quiz in December 2020 after the Mirror published a bombshell new photo from the event.
The Prime Minister's press secretary insisted the event was a "virtual quiz" but was unable to say whether the photograph had been submitted to Sue Gray's inquiry.
Former No10 aide Dominic Cummings, who has become a fierce critic of the PM, tweeted: "There's waaaaay better pics than that floating around, incl in the flat."
Defence Secretary Ben Wallace admitted today that new pictures could emerge at any time.
Scotland Yard has said punishments are likely to be limited to fines and it will not name people who received fixed penalty notices.
But Downing Street said it will inform the public if the Prime Minister receives a fine.
Mr Wagner told BBC Radio 4's Today programme that fixed penalty notices were the most likely penalty, "which can be issued when the police reasonably believe a person has committed a criminal offence".
He said: "There were 12 gatherings being investigated; the person we know was probably at six was the Prime Minister.
"So if he was given a fixed penalty notice for each and every one those, I think that he would be given those sort of cumulative amounts until eventually the final one would be £6,400.
"So overall, and assuming there isn't a big £10,000 one for hosting a gathering in the flat of over 30 people, he could still be in line for over £10,000 worth of fixed penalty notices if they accumulate".
Top Tory Ben Wallace admitted more pictures could appear - and claimed the leaking was "designed for a purpose".
Mr Wallace told Times Radio: "Yes, there could be a photograph tomorrow, the next day or the day after, that's clearly what's behind some of the people's motives.
"How accurate they are, how much they are put in the right context, that's what the police will find out."
In another interview he dismissed "media reports" that the police were contacting more than 50 people about Partygate - despite the Met Police explicitly saying so.
He said: "The PM has said he will be full and transparent. He will notify if he is receiving any form of fine etc but he has also said he will publish the Sue Gray report in full.
"So I think we let the police do that job and its investigation, we let it follow its task and in the meantime the Government will get on govern which it is elected to do."
In a statement on Wednesday, the Met said: "Detectives investigating allegations of breaches of Covid-19 regulations in Downing Street and Whitehall will by the end of this week begin contacting people believed to have taken part in the events in question to get their accounts.
"The officers, from what has been named Operation Hillman, will be sending formal questionnaires to more than 50 people.
"This document, which asks for an account and explanation of the recipient’s participation in an event, has formal legal status and must be answered truthfully.
"Recipients are informed that responses are required within seven days. In most cases contact is being made via email."
