A defence source said: “No obvious lessons have been learned from Kabul. It’s embarrassing. Leadership matters.”
James Cleverly, the Foreign Secretary, is expected to deliver an emergency statement on the latest developments in the Commons on Monday.
The Foreign Office’s current travel advice is for British citizens inside the country to register their presence via a form on its website and to shelter in place until an opportunity to leave safely presents itself.
It is not clear how many British citizens are still present in the country but it is likely to be at least in the hundreds.
Iman Abugarga, a British woman who had been sheltering in Khartoum, said she had followed advice to register but felt “absolutely” abandoned by the British Government and described communication as “shamefully mismanaged”
Britain is not alone in prioritising the evacuation of diplomatic staff.
The United States, which also evacuated its embassy on Sunday morning, said it has no plans for a general government-coordinated evacuation of American citizens trapped in Sudan.
But some other Western governments said they were seeking to evacuate all of their citizens.
The Irish government said it was “actively planning for assisted evacuation” of its citizens in Sudan. “We are currently in contact with more than 140 Irish citizens. Every effort is being made to assist them.”
However, the British defence source said: “The FO was terrified it would create another Kabul if we’d over-promised. 500 people would then become 5000 and we just can’t have that.”
The evacuation of Kabul descended into chaos, with a former civil servant later claiming the Foreign Office mishandled the process that led to dozens of deaths.
The evacuation of the British embassy in Khartoum involved 1200 personnel from the 16 Air Assault Brigade, the Royal Marines and the RAF, and was completed without any casualties.
A defence source, however, said there was “no real Foreign Office present”.
Mr Cleverly has acknowledged that Ambassador Giles Lever and his deputy were both away when the battles between the Sudanese army and the paramilitary Rapid Support Forces erupted.
“There was senior leadership still present in the embassy in Khartoum and actually having the ambassador in London, he was able to provide direct experience and knowledge to our crisis response unit that has proved to be invaluable,” he said.
Alicia Kearns, chairman of the Commons foreign affairs committee, said she was “uncomfortable” with diplomats leaving while British nationals remained apparently abandoned in Sudan, but she accepted there appeared to be no other option because of a “direct” threat to Western embassy officials.
She believed the plan would be to secure a ceasefire long enough to establish a land corridor for Britons to escape but said it involved the Government “being honest and open with British citizens”.
“The worst possible outcome is that the Government gives false hope. It needs to share its judgments and tell people we are working to get a ceasefire to evacuate or that like the US we are not going to evacuate our nationals and people can make their own decisions,” she said.
Tobias Ellwood, chairman of the Commons defence committee, said: “I hope we see a viable plan to help provide the rallying points and necessary transport to be able to evacuate all those who want to leave the country.
“There will be some who want to stay, who consider themselves Sudanese. But main British passport holders will want to get out and we have a duty of care to lean on our extended military assets to make that happen.”
Many Khartoum residents have attempted to flee overland to Egypt or the city of Port Sudan on the Red Sea coast. Both journeys take about 12 hours on roads that can be targeted by armed gangs.
A spokesman for the Foreign Office said: “The situation in Sudan continues to be complex and fast-moving.
“The ambassador to Sudan continues to lead a team around the clock, doing everything possible to keep British nationals safe. Any British national in Khartoum should register their presence with the FCDO to receive regular updates.
“Ultimately rival factions must commit to a lasting ceasefire to end this needless violence. The Foreign Secretary is engaged with international partners and we are using all diplomatic levers to demand a swift conclusion to the conflict.”
