Ben Wallace, who was to oversee Johnson's bid to be Prime Minister, says Gove is not fit to lead because he in an insatiable gossip, particularly while drinking.
He blames Gove for leaks of private information during Johnson's campaign, in a stinging Daily Telegraph article that ITV's Robert Peston called "worthy of a Tarantino blood fest".
Wallace, the Tory MP for Wyre and Preston North who worked with Gove when Gove was chief whip, said their office "leaked like a sieve" when they were colleagues.
"Important policy and personnel details made their way to the papers," he writes. "Michael seems to have an emotional need to gossip, particularly when drink is taken, as it all too often seemed to be."
Gove gave his support to Johnson's campaign to lead the Tory party - before sensationally ditching him to announce he would run for the role himself, which prompted Johnson to rule himself out of the running.
Wallace claims that "things started to go wrong" as soon as Gove joined Team Johnson, linking Gove to the leaking of confidential information, including camera crews arriving unexpectedly at Boris’ home, and the notorious email from Gove's wife Sarah Vine which questioned Boris's leadership potential.
He implies that Gove is untrustworthy, and doesn't understand that governing is "not a game, nor is it a role play of House of Cards."
Wallace, who is also a Northern Ireland minister, added that due to his work alongside the police and MI5 he knows that "In their world loose talk costs lives. It does in a prime minister’s world too.
"UK citizens deserve to know that when they go to sleep at night their secrets and their nation’s secrets aren’t shared in the newspaper column of the prime minister’s wife the next day, or traded away with newspaper proprietors over fine wine."
Commenters reacted with a mixture of shock and amusement to Wallace's bitter attack, with one calling it "brutal":
But others called Wallace out, accusing him of sour grapes and resorting to the petty move of implying Gove is "a girl" because he is unhappy that Boris's leadership race is over: