Sir Gavin Williamson has resigned as a government minister after allegations of bullying, saying he aims to clear himself of "any wrongdoing”.

The MP had been accused of sending abusive messages to a fellow Tory MP last month and of bullying a senior civil servant as defence secretary.

Sir Gavin said he "refuted" how his conduct had been characterised.

However, he added that the claims were becoming a "distraction" from the government's "good work".

In his resignation letter, he said he was leaving government with "real sadness" but offered Prime Minister Rishi Sunak his "full and total support from the backbenches".

He later tweeted he would not be taking any severance pay, adding that the money should go towards the government's priorities such as "reducing the NHS's waiting lists".

In reply, Mr Sunak said he accepted his resignation "with great sadness" and thanked Sir Gavin for his "personal support and loyalty".

"Your commitment to successive Conservative governments and the party over the years has been unwavering."

Sir Gavin had come under increasing pressure since a series of expletive-laden text messages sent by him to Tory colleague and then-Chief Whip Wendy Morton were published in the Sunday Times.

On Monday a senior civil servant told the Guardian Sir Gavin had bullied them and told them to "slit your throat".

And on Tuesday, Anne Milton, who worked as deputy chief whip between 2015 and 2017, told Channel 4 News that Sir Gavin's behaviour had been "threatening" and "intimidating".

Earlier, Downing Street said it had been seeking to establish the facts about the reported comments to the civil servant.

Sir Gavin had also been reported to the MPs' bullying watchdog - the Independent Complaints and Grievance Scheme (ICGS) - over his WhatsApps to Ms Morton.

The Guardian has reported that the senior civil servant who worked at the Ministry of Defence has also referred the MP to the watchdog.

In his resignation letter, Sir Gavin said he would comply with "an ongoing complaints process concerning texts he sent to a colleague" and added that he had "apologised to the recipient for those messages".

In the texts, he appears to complain MPs not "favoured" by then-Prime Minister Liz Truss were being excluded from attending the Queen's funeral at Westminster Abbey.

He apparently accused Ms Morton of "rigging" the ticket allocation to punish people - including himself - who were not supportive enough of Ms Truss.

Sir Gavin reportedly warned Ms Morton "not to push him about" and that "there is a price for everything".

Speaking on Monday, Mr Sunak said the language was "not acceptable" but asked if it amounted to bullying, he said it was "right" to let an independent complaints process conclude.

This is the third time Sir Gavin has left government. In 2019 he was sacked as defence secretary after details of Huawei's potential involvement in the UK's 5G network were leaked.

He was brought back to the cabinet, as education secretary by Boris Johnson, in 2019, but lost the job in 2021 following turmoil over A-Level exam results.

During the summer Sir Gavin helped run Mr Sunak's first campaign to become prime minister.

Following Mr Sunak's second, and this time successful, bid to become PM, Sir Gavin was given a job as a Cabinet Office minister.

Ex-Conservative Party Chair Jake Berry has said he told Mr Sunak about Ms Morton's complaint on 24 October - the day before Sir Gavin's appointment.

No 10 has said the prime minister "knew there was a disagreement" but he didn't know "the substance" of messages until they were published in the Sunday Times.

Labour's deputy leader Angela Rayner said: "This is yet another example of Rishi Sunak's poor judgement and weak leadership.

"As families struggle during a cost-of-living crisis made in Downing Street, yet another Tory government has descended into chaos."

Liberal Democrat Deputy Leader Daisy Cooper MP said: "Rishi Sunak has serious questions to answer about why he appointed Gavin Williamson, then stood by him instead of sacking him.

"His promise to lead a government of integrity has now been left in tatters."

The SNP's deputy leader at Westminster Kirsten Oswald said: "As the Westminster chaos continues to unfurl, there can be no doubt that independence is the only way to escape this dysfunctional system for good."