The wife of Brexit leader and Tory minister Michael Gove advised him to to secure "specific" concessions from Boris Johnson before "guaranteeing" that he will give him his full support in a leadership contest, leaked email correspondence suggests.
The email, which was apparently sent to a member of the public by mistake, urges him not to "concede any ground" with Mr Johnson in "crucial meetings" ahead of Mr Johnson's run to replace David Cameron as Prime Minister of the UK.
It claims that the membership of the Conservative Party "will not have the necessary reassurance to back Boris" without the support of Mr Gove.
Ms Vine, who writes for UK paper the Daily Mail but who met her husband while they both worked on The Times, suggests that Mr Gove needs to have one of his special advisers in the meetings to help him "thoroughly overcome individual obstacles".
The email, which was sent yesterday, says: "Very important that we focus on the individual obstacles and thoroughly overcome them before moving to the next. I really think Michael needs to have a Henry or a Beth with him for this morning's crucial meetings.
"One simple message: You MUST have SPECIFIC from Boris OTHERWISE you cannot guarantee your support. The details can be worked out later on, but without that you have no leverage.
"Crucially, the membership will not have the necessary reassurance to back Boris, neither will Dacre/Murdoch, who instinctively dislike Boris but trust your ability enough to support a Boris Gove ticket.
"Do not concede any ground. Be your stubborn best.
Journalist Kay Burley, who broke the story for Sky News in the UK, said the email made Ms Vine sound like Lady Macbeth. While the Guardian wrote: "There is nothing unusual about a wife, or husband, offering their spouse support but that "we" suggests that the Gove/Vine operation is something of a duopoly. It is very House of Cards."
Critics have also noted the passage which reveals that Mr Johnson does not have the full backing of the right-wing press. The Dacre she refers to is Paul Dacre, the editor of the Daily Mail, and Murdoch is Rupert Murdoch, who owns the Sun, The Times and The Sunday Times.
A spokesman for Mr Gove said: "We don't comment on private email exchanges or conversations."
A source close to Mr Gove said that the email represented Ms Vine's "personal opinion" and that "obviously Boris and Michael have had many discussions about how the campaign will proceed".
In her weekly Daily Mail coloumn, Vine gave an account of the night of the referendum in the Gove houselhold.
She wrote that her husband never expected or wanted Mr Cameron to resign as Prime Minister. Both she and Mr Gove were close friends of Mr Cameron and his wife Samantha and were god parents to his son Ivan. It is thought that Mr Gove's backing of the Leave campaign soured the couples' relationship, with Mrs Cameron said to be furious with her the former friends.
Here are extracts from the column:
There was a short pause while he [Michael Gove] put on his glasses. "Gosh," he said. "I suppose I had better get up."
I put the kettle on, began collecting wine glasses and loading the dishwasher. Upstairs, the shower sprang into life. I filled two mugs with our strongest brew and headed back upstairs. A morning like any other in the Gove household.
Except it wasn't. As I set the tea down on the bedside table, I tweaked the bedroom curtain aside and my suspicions were confirmed: several teams of reporters were waiting outside.
A quick flick of the remote control revealed a surreal scene: our house was live on Sky TV. Michael reappeared, towelling the water from his hair. By now his phone was buzzing and beeping like a demented frog.
"You were only supposed to blow the bloody doors off," I said, in my best (i.e. not very good) Michael Caine Italian Job accent. In other words, you've really torn it now.
By the time we got back to the car, coveted chicken and sweetcorn sandwich secured, the Prime Minister had resigned. I felt as though I had fallen through a rabbit hole - lost in a strange land where nothing made sense any more. This was absolutely, categorically not meant to happen.
David Cameron was not supposed to go. This was not what this referendum was about; that was not why Michael backed Leave.
This was a debate about Britain's membership of the EU, not a vote for or against the Prime Minister.
More than ever before, I felt the agony of what the business of politics had done to the people at the heart of all of this: how old friends had been wrenched apart in the most brutal of ways.
The way Remain campaigners have reacted to being unexpectedly on the losing side has shocked even a Twitter-hardened old hack like me.
I think it's because many of the most passionate Remainers are well-educated, articulate people in positions of authority, used to getting their own way.
Unlike your average troll, they don't rely on blunt invective to wound their opponents. Their anger takes the form of keenly worded, rapier-sharp attacks that cut deep.
Almost overnight, those of us on the winning side suddenly found ourselves re-cast as knuckle-dragging thugs, small-minded Little Englanders whose short-sighted bigotry had brought the nation to its knees, while making sweet Italian waitresses cry and stopping small Polish children from going to school.
Because of the immense power of the internet and social media, once a Twitterstorm reaches critical mass - which now happens at an alarming speed - it starts to become as real as thunder and lightning.
In a matter of hours, everything sunny about human nature seems to have been sucked out of the atmosphere and you are drenched in little 140-character balls of bitterness.
It's hard to explain quite what it feels like, but imagine walking into a room in a lovely new dress and having every single person turn, point, throw back their heads with laughter and tell you it looks hideous.
You'd never wear it again, would you? In fact, chances are you'd rip it up and throw it straight in the bin. There have been moments over the past few days when I've felt like that dress.
I have seen it happen to others - celebrities, sportspeople, household names - but I'd never imagined it happening to me. Such is the personal price of my husband standing up for his principles.
Read the full column here.