Cabinet minister Nadhim Zahawi has insisted he does not know who called a controversial meeting between Boris Johnson and Sue Gray over the senior civil servant’s pivotal partygate report.

The Education Secretary was repeatedly asked during broadcast interviews if he knew who had arranged the meeting and said he did not know but insisted the Prime Minister would “never intervene in Sue Gray’s investigation”.

The Prime Minister is facing pressure to “urgently explain” why the talks took place, with Labour arguing public confidence in the process had already been “depleted” and people “deserve to know the truth”.

It is understood the pair met at least once to give an update on the document’s progress while it was being drafted, but a Whitehall source said its contents were not discussed at any point.

The exact nature of the talks remains unclear.

Such meetings would not have been viewed as unusual, the source said, with the aim to take stock of what stage the report was at.

It was initially reported by the BBC that the discussions touched on whether photos would be revealed to the public and that Ms Gray initiated the meeting “to clarify her intentions” for what would happen once the police investigation concluded.

However, a spokesman for the Gray inquiry disputed this account of events.

A No 10 source insisted the request for the meeting did not come from Mr Johnson.

It has been reported the idea was in fact suggested by a No 10 official while the calendar invite was sent by Ms Gray.

This version of events was corroborated to the PA news agency by one source close to the inquiry, but uncertainty remains over the circumstances that led to the talks.

On Sunday, Mr Zahawi repeatedly failed to say who called the meeting between Mr Johnson and Ms Gray, conceding he did not know the answer.

He insisted the Prime Minister has “never intervened” in the senior civil servant’s investigation and Ms Gray’s integrity is “unquestionable”.

However, he was not able to say who called the meeting or what was discussed.

He told Sky News’ Sophy Ridge on Sunday programme: “All I can say to you is the meeting that took place between Sue Gray and the Prime Minister – I can’t tell you who called the meeting.”

The Prime Minister will never intervene in Sue Gray’s investigation. The Prime Minister wants Sue Gray to basically go wherever the evidence takes her

He later added: “I don’t know who called the meeting.” Asked what was discussed, he also said: “I don’t know.”

Asked if he could not say who called the meeting because he did not ask No 10, or because it did not tell him, Mr Zahawi said: “(I’ll) tell you what the answer is, the answer is very simple.

“The answer is the Prime Minister will never intervene in Sue Gray’s investigation. The Prime Minister wants Sue Gray to basically go wherever the evidence takes her.”

He later told the BBC’s Sunday Morning programme that he had not asked No 10 who called the meeting because he did not deem it necessary.

Asked if he had called Downing Street for clarification over the matter, Mr Zahawi said: “I don’t need to because I don’t believe that having a meeting with your senior civil servant is material to the outcome.

“That civil servant is independent in their investigation and has the highest level of professionalism and integrity.

“The Prime Minister has made it very clear that he has never intervened or will seek to intervene or interfere with the investigation.”

It comes as about 30 people, including Mr Johnson, are being contacted by the Cabinet Office to warn them of the contents of the document ahead of its expected publication next week.

It is thought that most of the letters were sent out on Thursday, as the Metropolitan Police concluded its investigation into lockdown breaches in Downing Street and across Whitehall.

Angela Rayner, Labour’s deputy leader, has called on the Prime Minister to “urgently explain” why the “secret meeting” with Ms Gray took place.

Downing Street insisted Mr Johnson had been “clear throughout” that the report should be “completely independent”.

Speaking to LBC on Sunday, International Trade Secretary Anne-Marie Trevelyan defended Ms Gray as “clear-headed” and “independent-minded”.

Like Mr Zahawi, she said she did not know who had organised the meeting with Mr Johnson, adding: “I don’t follow anybody’s diaries.”

Asked whether the details of who did call the meeting should be clarified to the public, she said: “I’m not sure that it makes any difference to me.

“I don’t think Sue is in any way likely to be someone who’s pushed around.

“She’s an amazing, very clear-headed, strong and independent-minded lady, and she will publish the report she feels is right, as the Prime Minister asked her to do originally.”

Labour’s shadow Treasury minister Pat McFadden said he had “every faith” in the senior civil servant’s integrity.

He told Sky’s Sophy Ridge on Sunday: “We don’t know the details of that meeting, it’s not clear who called it, there’s different accounts of that, so it’s hard for me to say what was said there.

“I do have faith in her integrity and let’s see what she says when the report comes out.”