Amar Idris said that his wife, Amina, 41, and daughter, Samrin, had fled fighting in Khartoum to travel to Port Sudan on the Red Sea.

The city’s airport hosted the UK’s last airlift from the country on Monday, which the mother and daughter had attempted to board.

But Idris said that British officials blocked Amina from boarding because she lacked a UK visa. They then told the mother that her daughter could not be placed on the flight alone.

He said: “This morning they (British diplomats) said they would take the child on the flight by herself. Then they came back and said they couldn’t take the child without her mother. They changed their mind.”

The mother and daughter had earlier left Khartoum after their home was struck in a bombing campaign. Samrin’s UK passport was left in the house during the chaos.

Idris warned that his wife’s health was “rapidly deteriorating” because she had gone without clean drinking water for several days.

Roza Mohamed, Samrin’s aunt, said: “I have contacted the Foreign Office four times and begged them to take Samrin.”

The UK government on Monday announced that it would end evacuation flights from the Wadi Saeedna airbase north of Khartoum amid a drop in British nationals applying for seats.

The diplomatic team in Port Sudan will now serve as the communication point for remaining British nationals seeking to leave the country by commercial means.

In a statement, Foreign Secretary James Cleverly hailed British evacuation efforts and praised embassy staff.

He said: “As the focus turns to humanitarian and diplomatic efforts, we will continue to do all we can to press for a long-term ceasefire and an immediate end to the violence in Sudan.”

Separately, a British Sudanese dual citizen from Birmingham, Adam Qumar Ibrahim, told The Times that his newly married cousin refused to board an evacuation flight from the country after his wife was refused entry.

Ibrahim’s cousin, Abbas Adam, had traveled to Sudan in February for his wedding, but had sought to leave the country along with his wife as fighting broke out between the government and Rapid Support Forces paramilitary.

Ibrahim said: “When the fighting started, he tried to come back to the UK and register himself and his wife with the Foreign Office.

“He spent three days in the airport, and they refused to take his wife. They said to him ‘if you want to go, we can take you but if you want to take your wife we can’t.’

“That is a very bad way of handling it. The British government should have believed them and brought them over and they can do the visa checks once they are safe.”

Saudi Arabia is playing a leading role in planning evacuation efforts from Port Sudan across the Red Sea.

Hundreds of refugees from Sudan, including 28 Britons, arrived in Jeddah on Monday on a US Navy vessel.

So far, more than 5,000 refugees have arrived in the Kingdom during international evacuation efforts.