Education Secretary Nadhim Zahawi has said he does not know who requested a meeting between the prime minister and Sue Gray over her partygate report, but is confident there was “no way” she would allow herself to be influenced by anybody.

Speaking to Sky News’ Sophy Ridge on Sunday programme, the cabinet minister also insisted Boris Johnson would not have intervened in the independent investigation.

He said the process had been “absolutely robust and rigorous”, pointing out the senior civil servant did not “pull her punches” in her previous limited report into lockdown-breaking parties in Downing Street, which criticised “failures of leadership and judgment”.

Pressure has been growing on No 10 to explain the meeting between Ms Gray and the PM, revealed by Sky News.

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 that its contents were not discussed at any point.

Opponents have demanded an explanation about the “secret meeting”, while a briefing war was sparked after sources initially claimed Ms Gray had initiated the meeting.

Her spokesman intervened to deny this, leading to a clarification by No 10 that it had not been ordered by the PM personally.

Mr Zahawi told Ridge: “I don’t know who called the meeting.

“What I do know is the prime minister doesn’t and never would never intervene in an independent inquiry,

He added: “Let’s not create this air of doubt around this process, which has been absolutely robust and rigorous.

Read more: PM to face investigation into whether he misled MPs about partygate

“I have no doubt about Sue Gray’s professionalism and integrity.

“There’s no way she would allow herself to be influenced by anybody.”

Labour’s shadow treasury minister Pat McFadden told Ridge: “I’ve got every faith in Sue Gray’s integrity and she is a civil servant of the highest integrity, 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.”