The UK Foreign Office's handling of the Afghan evacuation after the Taliban seized Kabul was "dysfunctional" and "chaotic", a whistleblower has said.
Raphael Marshall said the process of choosing who could get a flight out was "arbitrary" and thousands of emails with pleas for help went unread.
The then Foreign Secretary Dominic Raab was slow to take decisions, he added.
A government spokesperson said staff had "worked tirelessly" on the "biggest mission of its kind in generations".
And a source close to Mr Raab said verifying identity and securing safe passage had been the major practical challenge - not the speed of decision making.
The UK airlifted 15,000 people out of Afghanistan after the Taliban took control of the capital, Kabul. This included 5,000 British nationals, 8,000 Afghans and 2,000 children.
In written evidence to the Foreign Affairs Committee, Mr Marshall said up to 150,000 Afghans who were at risk because of their links to Britain applied to be evacuated - but fewer than 5% received any assistance.
"It is clear that some of those left behind have since been murdered by the Taliban," he added.
Mr Marshall, who was a senior desk officer at the Foreign, Commonwealth and Development Office (FCDO) until he resigned in September, said there was "inadequate staffing" at the department's crisis centre.
And there was a "lack...
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