LONDON -- The most senior civil servant at the British government's Home Office resigned Saturday and harshly criticized Home Secretary Priti Patel for her treatment of him.

Sir Philip Rutnam announced his resignation in a statement released by his lawyers and said he would be suing the government over his departure.

The Home Office did not immediately respond to a phone call seeking comment.

The resignation comes amid recent claims -- denied by Patel -- that she bullied staff.

"I have received allegations that her conduct has included shouting and swearing, belittling people, making unreasonable and repeated demands -- behaviour that created fear and that needed some bravery to call out," Rutnam said in his statement, which ended a 33-year career in Britain's civil service.

Patel was among ministers who held onto their jobs when Prime Minister Boris Johnson shook up his Cabinet on Feb. 13 following his sweeping election victory late last year.

Rutnam said that in recent days he was the target of a "vicious and orchestrated briefing campaign" amid allegations that he had briefed British media against Patel.

"This, along with many other claims, is completely false," he said.

Rutnam said he had tried to reconcile with Patel, but she had "made no effort to engage" with him.

"I believe that these events give me very strong grounds to claim constructive unfair dismissal, and I will be pursuing that claim in the courts," he said.

The head of the civil service, Cabinet Secretary Sir Mark Sedwill, said he had "received and accepted with great regret the resignation of Sir Philip Rutnam." Sedwill did not comment on Rutnam's claims about Patel.

Opposition lawmakers said the resignation laid bare failings in Johnson's government.

"Driving out of office a professional career civil servant is the clearest sign yet of the underlying right wing authoritarian but incompetent nature of the Johnson Government," senior Labour Party lawmaker Jon Trickett said in a tweet.