The denials came from Cabinet Office minister Michael Ellis as it was revealed the police questionnaire sent to Boris Johnson and Number 10 staff asks for a "lawful exception" or "reasonable excuse" for parties during lockdown.

The questionnaire, leaked to ITV News, says recipients have an opportunity to provide "a written statement under caution" and asks questions including the timings of attendance at parties and how many other people were present.

Downing Street confirmed last Friday that the prime minister has now returned his questionnaire to the Met. The questions in the document include:

• "Did you participate in a gathering on a specific date?"

• "What was the purpose of your participation in that gathering?"

• "Did you interact with, or undertake any activity with, other persons present at the gathering? If yes, please provide details."

The recipients are then asked: "What, if any, lawful exception applied to the gathering and/or what reasonable excuse did you have for participating in the gathering?"

Mr Ellis's denial of taxpayers' money being spent at the gatherings now under investigation came in reply to a written Commons question from Liberal Democrat MP Sarah Olney.

She asked: "Whether there was a cost to the public purse from expenditure on (a) alcohol, (b) food, (c) suitcases and (d) a fridge at gatherings being investigated by the (i) Second Permanent Secretary to Cabinet Office and (ii) Metropolitan Police?"

The minister, a criminal barrister and QC who has answered urgent questions on "partygate" in the Commons three times and displayed a coolness and aplomb which has frustrated Opposition MPs, simply told Ms Olney: "No."

The Cabinet Office inquiry referred to by the Lib Dem MP is a probe by civil servant Sue Gray, who is investigating 16 events. The Metropolitan Police is investigating 12 events, including as many as six the PM is reported to have attended.

One of the events being investigated was on 20 May 2020, when one of the PM's closest aides, Martin Reynolds, emailed staff saying "bring your own booze", a call which has earned him the nickname "Party Marty".

Read more: All you need to know about the Met Police's investigation

The suitcase in Ms Olney's question refers to a so-called "wheelie" case on a trolley which The Daily Telegraph claimed was taken to a Co-op supermarket on the Strand, filled up with bottles of wine and then wheeled back to Downing Street.

The fridge refers to a £142 refrigerator holding 34 bottles that the Daily Mirror reported was used to keep beer, prosecco and wine cool for "wine-time Fridays" held every week by staff in Downing Street, who were encouraged by the PM to "let off steam", it was claimed.

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Responding to Mr Ellis's denial that taxpayers' money was spent on parties, Ms Olney said: "The fact that a question needs to be asked is a damning indictment of the prime minister.

"This whole time, people have stuck to the rules and made enormous sacrifices to protect others. Meanwhile this prime minister has with one hand made the rules and with the other is under criminal investigation for breaking them."

In an interim report last month, Ms Gray said: "The excessive consumption of alcohol is not appropriate in a professional workplace at any time.

"Steps must be taken to ensure that every government department has a clear and robust policy in place covering the consumption of alcohol in the workplace."

In recent months the Cabinet Office has faced a number of written questions from Opposition MPs relating to the "partygate" affair seeking to establish if public money was involved.

Labour's shadow attorney general Emily Thornberry asked if government procurement cards were used to make purchases lower than £500 at the Co-op on 16 April, the night of the alleged suitcase trip. Mr Ellis again replied: "No."

Read more: Which Conservative MPs have called on the prime minister to quit?

In another question, Ms Thornbury asked if public funds were used to buy fridges for use in Downing Street in the financial year 2020/21.

This time Mr Ellis responded: "Downing Street is a working building, including catering facilities and offices for staff; as is common in workplaces including the House of Commons, refrigerators are provided for general staff use.

"One refrigerator was purchased in the financial year for a Downing Street meeting room, and one to replace an existing refrigerator that had reached the end of its working operation.

"Notwithstanding, I can confirm that no such public expenditure was accrued in relation to the matters considered in the investigations by the second permanent secretary or connected with associated media reports on this matter."