The Chancellor’s scathing assessment on the former Foreign Secretary came on Sunday, on the eve of his speech to the Tory Party conference in Birmingham.
In a withering slight, Mr Hammond said his former Cabinet colleague was utterly clueless on his how own proposals for a Brexit deal would work.
He also claimed Mr Johnson was doomed to fail if he attempted to succeed Mrs May as Tory leader.
Mr Hammond told the Daily Mail: “I don’t expect it to happen.”
The seething tirade is a sign of the growing anger in Mrs May’s Cabinet towards Mr Johnson’s outspoken criticism of her Brexit approach.
Divides within the Conservative Party are becoming increasingly pronounced as factional groups such as the European Research Group, spearhead by Mr Johnson and Jacob Rees-Mogg, threaten to topple Mrs May.
The divides could turn the Conservative Party conference sour this week, as members meet to discuss their vision for the future.
During an extraordinarily unguarded interview, Mr Hammond attempted to downplay his “fiscal Phil” and “Eyeeore” image by impersonating Mr Johnson’s trademark rhetoric, stammering speech and plummy vowels.
When questioned about Mr Johnson’s attack on Mrs May’s Chequers plan as “supine” and “deranged”, Mr Hammond said: “Boris is a wonderful character, but he’s never been a detail man.
“I’ve had many discussions with him on Brexit.
“Boris sits there and at the end of it, he says ‘yeah but, er, there must be a way, I mean, if you just, if you, erm, come on, we can do it, Phil, we can do it.
“‘I know we can get there.’ And that’s it!”
Mocking the Old Etonian, Mr Hammond said: “‘We just have to want it a bit more, we just have to wish a bit harder, we just have to be a bit more bullish and it will all be fine.’
“But it won’t all be fine because we are dealing with grown-ups here and we have to deal with the real world situation we face.”
The news comes as Mrs May railed against her former Cabinet colleague for questioning her commitment to leaving the EU and as Mr Johnson ramped up his rhetoric against her Chequers deal.
Former Brexit Secretary David Davis has admitted brinkmanship by the EU would result in a “very scary few months” – but he also claimed there was an 80-90 percent chance a Brexit deal will be struck.
Environment Secretary Michael Gove has also indicated he is open to a Canada-style trade deal if the EU rejects Chequers.
Mrs May joined a standing ovation for former CBI chief Digby Jones after he labelled Mr Johnson as “irrelevant and offensive”.
In a clear putdown, Mr Hammond said Mr Johnson’s greatest political achievement to date was “Boris Bikes” during his time as London mayor – a scheme which was originally the brainchild of Ken Livingstone.
The Chancellor said Mr Johnson’s “political experience is the triumph of will, of personality, that’s his experience as London mayor.
“What were Boris’ policies as mayor?
“You can think of one or two like Boris bikes.
“But I’m afraid when you are negotiating with the EU, you have to look at the facts and details.
“It was vital to understand the EU’s position to have any hope of reaching an agreement with them.
“That’s not supine, that’s not capitulation.
“Anyone who’s ever done any negotiation will tell you it’s just simple common sense that you need to understand the position of your opponent to negotiate effectively with them.”