Rishi Sunak has “full confidence” in the Cabinet Office minister Gavin Williamson despite the emergence of bullying claims and abusive text messages he sent to the former Conservative chief whip Wendy Morton. The texts were revealed over the weekend to include angry remonstrations about not being invited to the Queen’s funeral and one that said “there is a price for everything”. On Monday the prime minister’s spokesperson said Sunak had a zero-tolerance approach to bullying, but had refused to sack Williamson, claiming he had an “important contribution to make to government”. No 10 has been unable to spell out Williamson’s current responsibilities as a Cabinet Office minister. Asked if the prime minister had full confidence in Williamson, the spokesperson said: “Yes.” Pressed on why Sunak gave Williamson a job, he added: “Obviously he thinks he has an important contribution to make to government.” Sunak is facing mounting criticism over his decision to bring Williamson back into the cabinet with knowledge of Morton’s claims. Meanwhile the Times reported on Monday that Williamson, as chief whip in 2016, threatened a now minister with potentially revealing details about her private life. She told the paper that Williamson called her to his office when she was campaigning on a politically sensitive issue and raised something about her private life “which she interpreted as a tacit threat”. Unnamed “allies” of Williamson said this had not been a threat, and that he had raised the issue in a “pastoral capacity”. No 10 says Sunak has “welcomed” that Williamson has “expressed regret” for sending the text messages to Morton. When asked why Sunak decided to give Williamson a seat at the Cabinet table, the PM’s spokesperson said Sunak “was aware of a complaint”, adding: “He knew there was a disagreement but didn’t know the substance of those messages.” The PM’s spokesperson said he was “not aware” whether Sunak had spoken with either Williamson or Morton since the matter came to light, but stressed he would not normally get into details of private conversations. Sunak brought back Williamson to the frontbench as a junior Cabinet Office minister. On Sunday, the prime minister said that while he was aware Morton had made a complaint about Williamson, he had not seen the messages beforehand. “I hadn’t seen those texts before last night, I had not,” Sunak told the Sun newspaper in an interview en route to the Cop27 climate summit in Egypt. “I was aware there was a disagreement between him and the former chief whip.” Labour and the Lib Dems have called for Sunak to sack Williamson. Sunak said the messages were “not acceptable or right”, but did not say if he would take any action. “It was a difficult time for our party at the time, but regardless, people always should be treated with respect,” Sunak said. “I am glad Gavin has expressed regret. There is an independent complaint process, which is running. It is right and reasonable we let that conclude.” Grant Shapps has added to the condemnation of Williamson’s abusive text messages to a colleague, saying the messages should not have been sent. Shapps told Sky News: “I don’t think it was the right thing to do, to send messages like that. I see they must have been sent in a moment of frustration. I think, generally, it is the case that it’s much better to write things which you would not live to regret later. “And especially with colleagues, writing things which are polite, even if you have a point of view to express, I think is not unreasonable. So, I don’t think he was right to send them. The prime minister said the same. I know that the party is going through a process looking at them at the moment.” Morton is said to have cited the messages from Williamson in an email to the party on the day before Sunak was elected leader. She is also said to have informed the Cabinet Office and accused Williamson of “bullying and intimidation”. After he was not among ministers or former ministers invited to attend the Queen’s funeral, Williamson texted Morton saying it was “very poor and sends a very clear message” that members of the privy council who were not “favoured” by Truss were being deliberately excluded, and said it looked “very shit”. “Also don’t forget I know how this works so don’t puss [sic] me about,” he wrote. “It’s very clear how you are going to treat a number of us which is very stupid and you are showing fuck all interest in pulling things together,” one message said. “Don’t bother asking anything from me.” Another read: “Well let’s see how many more times you fuck us all over. There is a price for everything.” Williamson was sacked first by Theresa May as defence secretary for leaking details of a national security council meeting and then by Boris Johnson as education secretary over the Covid-19 A-levels debacle. He was seen as a key figure in Sunak’s campaign over the summer to become party leader.