Boris Johnson's new communications chief accused the Prime Minister of "digging his political grave" with ill-judged remarks.
Guto Harri - who was Mr Johnson's communications director for four years while he was Mayor of London - made the remarks in 2018, after his old boss compared Theresa May's Brexit deal to a "suicide vest".
He also referred to reports of Mr Johnson's numerous affairs, saying: "Unfortunately he is now dragging us into a place where we think that we can joke about suicide vests and that we can be sexually incontinent."
He told the BBC : "Somebody needs to take the spade out of his hand or it looks to me like he’s digging his political grave."
Number 10 announced Mr Harri's appointment as Communications Director this evening, alongside Tory minister and loyalist Steve Barclay, who will become the PM's chief of staff.
"He was a huge unifying figure by the end of my time with him when the Olympics happened in London," Mr Harri said of Johnson in the 2018 interview.
"He would not have been re-elected in a left-leaning city like London if he hadn’t appealed to the left."
He added: "Now he’s gone the other way. He’s become more tribal, and tribal within the tribe, so that he would now be — if he were to become leader — a hugely divisive figure."
Mr Harri was suspended from and later quit a presenting job with GB News after taking the knee on air.
