Rishi Sunak has said threatening and abusive texts sent by Sir Gavin Williamson to a colleague were “not acceptable or right” as he insisted he had been aware of a “disagreement” but not the details of the exchange.

The Prime Minister is under fire for bringing Sir Gavin back into the Government despite being warned that he was under investigation for allegedly bullying former chief whip Wendy Morton.

On Sunday evening, Mr Sunak told The Sun: “I hadn’t seen those texts before last night, I had not.

“I was aware there was a disagreement between him and the former chief whip.”

Former Conservative Party chairman Sir Jake Berry informed Mr Sunak on the day he took office that Ms Morton had lodged a formal complaint over the messages.

In them, Sir Gavin angrily accused her of seeking to “punish” MPs like him who were out of favour with Liz Truss by excluding them from the Queen’s funeral.

The exchange of texts, obtained by The Sunday Times, concluded with him saying: “Well let’s see how many more times you f*** us all over. There is a price for everything.”

Mr Sunak said: “They were not acceptable or right.

“It was a difficult time for our party at the time, but regardless, people always should be treated with respect.

“I am glad Gavin has expressed regret.

“There is an independent complaint process which is running, its right and reasonable we let that conclude.”

Earlier, Cabinet Office Minister Oliver Dowden – one of Mr Sunak’s closest allies – insisted that the Prime Minister still had confidence in Sir Gavin, who is now also a minister in the Cabinet Office.

“As you have seen from the former chairman Jake Berry, he says that he highlighted that to the Prime Minister,” he told Sky News’s Sophy Ridge On Sunday programme.

“But in terms of the specific allegations, the specific exchange, the Prime Minister wasn’t aware of it until last night.”

However, Labour said it once again raised questions about Mr Sunak’s judgment after he reappointed Suella Braverman as Home Secretary just six days after she was forced to quit over a security breach.

Shadow climate change secretary Ed Miliband told Sky News: “These are incredibly serious issues and I think it really calls into question Rishi Sunak’s judgment and the way he made decisions about his Cabinet.”

In the messages, Sir Gavin complained it was “very poor” that MPs who “aren’t favoured” had been excluded from the funeral of the Queen at Westminster Abbey.

Ms Morton repeatedly insisted that his claims were unfounded and that the Government had been allocated an “extremely limited” number of tickets.

Sir Gavin retorted: “Well certainly looks it which think is very shit and perception becomes reality. Also don’t forget I know how this works so don’t puss (sic) me about.

“It’s very clear how you are going to treat a number of us which is very stupid and you are showing f*** all interest in pulling things together.

“Also this shows exactly how you have rigged it is is (sic) disgusting you are using her death to punish people who are just supportive, absolutely disgusting.

“Well let’s see how many more times you f*** us all over. There is a price for everything.”

Sir Jake told the paper that he was informed by the Conservative Party chief executive on October 24 – the day before Mr Sunak formally took office – that a formal complaint had been made against Sir Gavin.

“In compliance with protocol, in my capacity as party chairman, I informed both the new Prime Minister and his incoming chief of staff about the complaint on the same day,” he said.

Sir Gavin, who was knighted by Boris Johnson earlier this year, is a divisive figure at Westminster where he is viewed with suspicion by many Tory MPs because of his reputation as an inveterate plotter.

He was sacked first by Theresa May as defence secretary for leaking details of a National Security Council meeting and then by Mr Johnson as education secretary over the Covid-19 A-levels debacle.

However he was regarded as a key figure in Mr Sunak’s campaign over the summer to become party leader.

A Conservative Party spokesman: “The Conservative Party has a robust complaints process in place.

“This process is rightly a confidential one, so that complainants can come forward in confidence.”