Mercer was reportedly sacked by text after being summoned to see the Chief Whip, Mark Spencer, last night after expressing frustration at a lack of progress on legislation to protect British veterans who served during the Troubles from prosecution.
Spencer told Mercer he had to resign there and then so as not to create any more fuss, and he’d “get a nice letter” from the PM if he did. Mercer told the Chief Whip to “f*** off”, and walked out.
Ten minutes later, the Chief Whip texted Mercer to inform him that he had been relieved of his duties. The PM wrote him a nice letter anyway.
Mr Mercer said on Wednesday that “nothing has been done” over the “gross betrayal of people who signed up to serve in the military”, as he gave a damning account of Boris Johnson’s Government.
“This is the most distrustful, awful environment I’ve ever worked in, in Government. Almost nobody tells the truth, is what I’ve worked out over the last 36 hours,” he told Times Radio.
The MP for Plymouth Moor View said that he was “made to feel like I’m the last man in the room who’s willing to fulfil our manifesto commitments”, as he described politics as a “cesspit”.
“You know, I find this place has taught me a lot about the Government, a lot about my colleagues: let’s say shooting straight is not one of their finest qualities,” he added.
Earlier in the day, former Scots Guards captain Leo Docherty was appointed as Mr Mercer’s successor.
Defence Secretary Ben Wallace said he is “delighted” to welcome Mr Docherty to the department.
“He will be taking up one of the most important roles, championing our veterans and service personnel,” Mr Wallace said.
Mr Mercer had been heavily involved in the Overseas Operations (Service Personnel and Veterans) Bill, which was being considered by MPs on Wednesday as it goes through its final stages in Parliament.
The legislation was developed in response to legal claims made after operations in Iraq and Afghanistan, but does not cover incidents in Northern Ireland.
In his resignation letter, he wrote: “It is with a heavy heart that I am forced to offer you my resignation from government.
He added: “I remain genuinely appalled by the experiences of some of the nation’s finest people who have served in the Armed Forces.
“I fought and bled alongside them. I’ve been far more fortunate than many of them since and I have a duty to tell their truth to power.”
He said that many veterans have been sectioned or drunk themselves to death because the government cannot find a political solution to “the appalling injustices” they faced.
Mr Mercer said in the letter to the Prime Minister that not including those who served during the Troubles was his “red line”, adding: “They are not second-class veterans. They deserve the protections of the Overseas Operations Bill like everyone else.”
Mr Johnson said in his reply to Mr Mercer that he was “grateful” for his contribution as veterans minister and that he had “made a real difference” to the lives of defence personnel and veterans.
He said the Overseas Operations Bill is a “crucial part” of efforts to protect personnel against “vexatious and repeated” legal claims.
“But we are committed to doing more over the coming months, including for those who have served in Northern Ireland,” he said.
Additional reporting by PA.