Sir Philip Rutnam, the top civil servant at the Home Office, has quit following a series of run ins with Home Secretary Priti Patel.
He read a statement on BBC News which said: "I have this morning resigned as permanent secretary of the Home Office. I take this decision with great regret after a career of 33 years.
"I am making this statement now because I will be issuing a claim against the Home Office for constructive dismissal.
"In the last 10 days I have been the target of a vicious and orchestrated briefing campaign.
"It has been alleged that I have briefed the media against the Home Secretary.
"This along with many other claims is completely false."
Sir Philip went on: "The Home Secretary categorically denied any involvement in this campaign to the Cabinet Office.
"I regret I do not believe her. She has not made the effort I would expect to dissociate herself from the comments.
"Even despite this campaign I was willing to effect a reconciliation with the Home Secretary.
"But despite my efforts to engage with her, Priti Patel has made no effort to engage with me to discuss this.
"I believe these events give me very strong grounds to claim constructive, unfair dismissal and I will be pursuing that claim in the courts."
