Emily Thornberry, the shadow foreign secretary, spoke out as it emerged that the prime minister will not return to work until Monday – almost two weeks after he flew to the paradise island of Mustique.
“He’s sunning himself, drinking vodka martinis somewhere else, and not paying attention to this,” Ms Thornberry told Sky News’ Sophy Ridge on Sunday programme.
In a separate newspaper article, the Labour leadership contender, suggested the prime minister was staying silent because he was “afraid of angering Trump”.
The attack came as Dominic Raab, the foreign secretary, admitted Mr Johnson would not be “back in play” until Monday, after flying back over the weekend from the luxury break with Carrie Symonds, his girlfriend.
Mr Raab insisted he had been in “constant contact”, to discuss the crisis, adding: “What really matters is that there is a very clear strategy and message.”
“There has not been a vacuum at all – the prime minister has been in charge,” he told the BBC’s Andrew Marr programme.
In the interview, Ms Thornberry warned of a “lurch towards war” because of Donald Trump’s “reckless” decision to kill General Soleimani, moments after Mr Raab gave the UK’s backing.
She said she “sheds no tears” for the military leader but added it was “not making the world safer,” warning British interests in region are “now vulnerable”.
“To take him out at this stage, when there has been escalating tensions, seems to me to be not making the world safer, actually we are taking a major lurch towards war, Ms Thornberry said.
“And we are doing that because the president is reckless and hasn’t thought through what it is he is doing.
“But it seems to me quite clear that the Iranians are going to counter-attack and it means that our interests, our people, our forces are, of course, under threat.”
The shadow foreign secretary also pointed to Mr Trump’s failure to notify the UK before carrying out the fatal drone strike on Friday, as evidence of London’s lack of influence.
“He didn’t even tell us before he agreed for this man to be killed in Baghdad,” she said. “They breached Iraqi sovereignty in order to kill the head of the defence forces for Iran.
“There will be great pressure on the Iraqis to say to the Americans and to the British and to the other Western allies that have been trying to help them fight Isis that they should leave, and so I think that it makes the whole area much more unstable, much more dangerous.”