Boris Johnson could return a police questionnaire into No10 lockdown parties blank, according to a legal expert.
The Metropolitan Police sent him the form as part of a probe, named Operation Hillman, into 12 parties in Downing Street.
Officers have contacted 50 partygoers, with the PM believed to have been at six of the parties under investigation.
Now senior law lecturer Dr Nick McKerrell has told the BBC that Mr Johnson may be able to return the questionnaire blank.
He said: "Doing a questionnaire is quite weird because you don't have that interaction in the same way.
"So theoretically, you could get no information from the questionnaire, because one of the rights you've got when questioned by the police is the right to remain silent.
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"So you could return a blank form, I think in a criminal investigation, and it would have weight behind it. So it's an unusual thing to do in a criminal investigation."
The Glasgow Caledonian University lecturer said the questionnaire might be "filtering" in order for the police to establish where to conduct more direct interviews later.
Another issue would be the length of time which had passed since the alleged offences and the fact the maximum penalty would be a fine, he said.
Dr McKerrell said: "This causes this major problem, about how do you speak to someone over things that happened months ago, when the maximum offence is a fine?
"So that's one of the issues behind it, but it won't solve the issue, it I think will have to lead to some form of more direct investigation to just get the information."
A No 10 spokesperson said: "We can confirm the Prime Minister has received a questionnaire from the Metropolitan Police. He will respond as required."
Mr Johnson is expected to personally hire his own private lawyer who will guide him on how to respond to the questions.
The PM’s lawyer may focus on the “unique” situation of Downing Street being Mr Johnson’s workplace and his home.
The Met has warned the forms have “legal status and must be answered truthfully”.
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Chancellor Rishi Sunak suggested he does not expect to be contacted by police - despite previously confirming he attended a birthday do for the PM organised by his wife Carrie Johnson.
The Mirror understands the Prime Minister has seven days to respond, outlining his “reasonable excuse” for why his attendance at the parties did not break the Covid laws he set.
The Chancellor said he had been present at the Cabinet Room on the day in question for a routine Covid meeting.
Mr Sunak told Sky News he had not received a questionnaire from the Met and, asked whether he expected to receive a form to complete, he replied: "No... well, I don't know."
The Treasury chief also said he did not think he had broken Covid rules.
