Just 5% of Afghan nationals who applied for help to flee the country under one UK scheme after the Taliban swept to power received help – with some left behind having been murdered since the collapse of Kabul, a whistleblower has claimed.

In evidence published by the Foreign Affairs Select Committee on Tuesday, Raphael Marshall – who worked for the Foreign, Commonwealth and Development Office (FCDO) during the evacuation effort – told how at one point he was the only person monitoring an inbox where pleas for help were directed.

He said although the Government made public statements over hopes the Taliban had changed in attitude and approach, this did not tally with the information he was receiving.

Mr Marshall’s written evidence is due to be published by the committee on Tuesday, and its chairman, Conservative MP Tom Tugendhat, said the “failures betrayed our friends and allies and squandered decades of British and Nato effort”.

And he said it painted the evacuation as “one of lack of interest, and bureaucracy over humanity”.

Mr Marshall worked in the Afghan Special Cases team, which handled the cases of Afghans who were at risk because of their links with the UK, but who did not work directly for the UK Government.

He estimated that “between 75,000 and 150,000 people (including dependants) applied for evacuation” to the team under the leave outside the rules (LOTR) category.

And he estimated that “fewer than 5% of these people have received any assistance” and states that “it is clear that some of those left behind have since been murdered by the Taliban”.

He said that no member of the team working on these cases had “studied Afghanistan, worked on Afghanistan previously, or had a detailed knowledge of Afghanistan”.

And that junior officials were “scared by being asked to make hundreds of life and death decisions about which they knew nothing”.

Former foreign secretary Dominic Raab said he did not recognise figures from the whistleblower.

Mr Raab, who is now Deputy Prime Minister and Justice Secretary, told Sky News it was “right” the UK had a process in place to check for those at “genuine risk of persecution” and protect the country from potential threats.

Asked if he recognised the whistleblower’s figures, he said: “I don’t. But what is certainly true is that we had a lot of people rushing to get out of Afghanistan for all sorts of reasons.

“And I think it’s right that we had a process in place to check two things: One, that we were helping those at genuine risk of persecution, or British nationals or people who had worked for the British Government.

“And secondly, making sure that we didn’t allow anyone to come into the UK who might present a threat to the UK.

“And it was important to have a process to make those decisions swiftly but also accurately.”