A former head of the Army has slapped down Dominic Raab for being on a beach holiday while Kabul fell to the Taliban.
Lord Dannatt said the top Tory should've realised he needed to "get back and show some leadership".
The Foreign Secretary stands accused of going "missing in action" when the situation in Afghanistan's capital was spiralling out of control.
He was spotted at a five-star resort on the Greek island of Crete on Sunday as the Taliban marched into the capital. Reports claim he only left in the evening - arriving back in London after 1am.
That is despite Taliban forces storming into the Afghan capital through the day on Sunday, 20 years after being ousted by the West in the war on terror, and advancing towards it for several days beforehand.
As images showed desperate Afghans falling to their deaths from a US plane, Mr Raab defended his holiday - saying he deserved a break after "two years of a very gruelling demanding schedule" and he arrived back in the UK "as soon as the situation deteriorated and demanded it".
He claimed he'd already been working from his beach outpost. But he also admitted if he'd known the Taliban would take Kabul on Sunday, he wouldn't have gone away at all.
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Despite the Taliban advancing across Afghanistan for days before, he claimed: "No one saw this coming. Of course we’d have taken action if we had."
But Lord Dannatt, Chief of the General Staff from 2006 to 2009, told Times Radio: "There appears to be a deafening silence from the Foreign Office.
"Okay, the Foreign Secretary was on holiday, everyone’s allowed to go on holiday.
"But when there’s a crisis of this magnitude I think that’s the moment you unfortunately have to cut short your holiday, get back and show some leadership."
The former Army chief added: "The government’s response has been very, very slow. Even when we published an open letter three weeks ago, signed by 45 retired senior military officers, the government's response to that has been pretty slow.
"They’ve been overtaken by events, their response has been slow, and it’s not been a great look for British defence."
Boris Johnson was also away on holiday in the West Country as Kabul started to fall, raising questions about who was in charge of the UK response to the crisis.
Mr Johnson is understood to have travelled to the West Country for a staycation on Friday night, while Mr Raab is thought to have been near the end of his Greek break.
Keir Starmer has piled further pressure on the Tory pair for holidaying while Afghanistan fell.
"It was completely wrong to be on holiday. Speak to anybody who has any experience of Afghanistan and they will tell you it was obvious last week that we were heading to a very serious situation," Labour's leader said.
"For the Prime Minister and the Foreign Secretary to be missing in action at this vital time is something that everybody thinks is wrong."
Earlier Mr Raab admitted the UK Government did not see the Taliban takeover of Afghanistan coming.
The Foreign Secretary admitted that several nations were "caught off-guard" by the quick and hostile nature of the militant group's takeover, which has prompted Afghans to flee the country.
He claimed British intelligence had been tracking what was happening on the ground in Afghanistan "very carefully" after the United States decided to reduce its troops in the country.
He admitted that Britain will have to engage with the Taliban in the future in order to hold them to account for their actions.
But Mr Raab has refused to rule out sanctions against the Taliban if they fail to cooperate internationally.
He suggested the UK could increase aid funding to the Afghan people - just months after slashing it by millions of pounds.
Speaking to Sky News, Mr Raab said: "The truth is, across the world, people were caught by surprise. I haven't spoken to an international interlocutor, including countries in the region over the last week, who hasn't been surprised. We saw a very swift change in the dynamics, and of course this has been part and parcel of the withdrawal of Western troops, but it has also been the way and the approach of the Taliban.
"Of course it's been a test for the Afghan security forces. All of those factors have been very fluid. But no one saw this coming. Of course we would have taken action if we had."
Boris Johnson is calling for high-level international discussions on the unfolding crisis, including using the UK's G7 presidency to call a virtual meeting in the coming days.
The PM will address Parliament on Wednesday after MPs were recalled to discuss the urgent situation unfolding in Afghanistan.
But the Mirror understands the title of the debate is set to be "that this House has considered the situation in Afghanistan".
That will mean the Prime Minister will be able to avoid answering detailed questions or a firm vote by MPs.
