David Cameron felt “badly let down” by Theresa May during the EU referendum campaign, his former communications chief has said.
Sir Craig Oliver, a former key aide to Mr Cameron, said the former PM became intensely frustrated at Mrs May’s unwillingness to declare her intentions in the run-up to the campaign.
He said Mrs May failed to support Mr Cameron on 13 separate occasions before she did reluctantly "come off the fence" for Remain - and then only after a "visibly wound up" prime minster gave her a dressing down over the telephone.
In his book, Unleashing Demons: The Inside Story Of Brexit, serialised in The Mail on Sunday, Sir Craig also describes Boris Johnson's "flip-flopping" during the weekend he finally came out in support of Brexit.
He said that the day before he made the announcement putting himself at the head of the Vote Leave campaign, the former London mayor warned Mr Cameron in a text he would be campaigning for Out, only to send a second text suggesting he could change his mind.
Sir Craig said Mrs May's unwillingness to declare her hand in the run-up to the campaign had caused frustration in No 10, but he admitted that her low-key approach served her well in the aftermath of the vote for Brexit.
"Amid the murder and betrayal of the campaign, one figure stayed very still at the centre of it all - Theresa May. Now she is the last one standing," he wrote.
He describes one conversation with Mr Cameron in January - six months before the referendum - after the then prime minister had sought to sound out Mrs May - who was then home secretary - about her views on the EU.
"It sounds like she refused to come off the fence. From her point of view it's a smart strategy, trying to demonstrate she is her own person, allowing her to have her cake and eat it, but it doesn't seem fair on DC, who has treated her well," he wrote.
There was further consternation within No 10 when during a Cabinet discussion on the issue, Mrs May did not join in, "playing her cards close to her chest".
"Her sphinx-like approach is becoming difficult, with the press questioning which way she will jump. The conversation turns around this being the biggest thing the PM has faced and him not even knowing if the home secretary is backing him," he wrote.
Matters finally came to her after a report in The Times warning that Mr Cameron faces "last minute opposition" from Mrs May to his deal on EU reform.
"Later, on a train to Chippenham for a speech, DC is visibly wound up by the report. Suddenly he picks up his mobile and calls May, asking her to make clear we have been victorious in our plan to crackdown on 'swindlers and fiddlers' attempting to come into the UK," Sir Craig wrote.
"When he hangs up he seems to think he's made an impact. Later the Home Secretary issues a statement saying she believes there's 'the basis for a deal here'.
"This is interpreted as the moment she climbed down off the fence. After all the concern around her, it all seems to have ended not with a bang , but a whimper."
Additional reporting by Press Association.
