MinterEllison chief executive Annette Kimmitt has left the the law firm after its board decided her position was no longer tenable in the wake of an email she sent to staff about the firm acting for Attorney-General Christian Porter.

The firm’s chairman, David O’Brien, wrote to partners just before 10pm on Wednesday advising them that Ms Kimmitt had worked her last day after they had “mutually agreed” on her departure.