In a blow to British Prime Minister Rishi Sunak, his close aide and Deputy Prime Minister Dominic Raab resigned on Friday amid allegations that he bullied staff members while working as a cabinet minister across different UK government departments.

Sunak had been handed the independent report into allegations made by several civil servants on Thursday and a decision on Raab, who is also the UK Justice Secretary, was anticipated ever since.

In his resignation letter posted on Twitter, Raab, 49, revealed the report into his conduct had upheld two claims against him.

However, he did call them "flawed" and claimed they set a dangerous precedent of a low threshold for bullying for the conduct of good government.

"Whilst I feel duty bound to accept the outcome of the inquiry, it dismissed all but two of the claims levelled against me,” writes Raab.

"I also believe that its two adverse findings are flawed and set a dangerous precedent for the conduct of good government," he said.

"In setting the threshold for bullying so low, this inquiry has set a dangerous precedent. It will encourage spurious complaints against ministers, and have a chilling effect on those driving change on behalf of your government – and ultimately the British people," he added.

Sunak had come under pressure soon after he appointed Raab, a staunch supporter of his leadership for the Conservative Party and government during the campaign last year, to the two key Cabinet posts as the bullying allegations emerged.

Downing Street said at the time that Sunak was "not aware" of any formal complaints against Raab when he appointed him in October last year.

However, the Opposition Labour Party accused Sunak of ignoring reports about Raab's conduct.

Raab's exit will now necessitate a mini shuffle in the Cabinet, as reports indicate that Sunak may not refill the post of Deputy PM and only appoint a new Justice Secretary.