The former prime minister was speaking after viewing a Sky News report from the Taliban-run country, showing "malnourished, horribly weak" children and a toddler who had frozen to death.

Multiple aid organisations fear millions of Afghans could starve as the winter progresses.

Mr Brown said it was "quite shocking" that the West was yet to respond effectively. "I wrote to the foreign secretary weeks ago and I'm waiting for a reply," he told Sky News.

The United Nations says $4.4bn (£3.2bn) is needed for humanitarian purposes.

"Britain gave just over 90 million last week but that is not enough," Mr Brown said, describing the crisis as a "matter of hours and days, not a matter of months and years".

He dismissed the idea that the Taliban would appropriate money or supplies, saying that NGOs and UN organisations can get aid through.

Dr Paul Spiegel, former deputy director of the UNHCR, spent five weeks in Afghanistan before Christmas.

"What we saw was quite devastating," he told Sky News. "The economy is in complete ruins, and that also relates to all of the hospitals."

Because of sanctions, many provincial and regional hospitals are not allowed to receive funding because they are run by the government, Dr Spiegel said.

Most of the facilities do not have basic materials or oxygen, he added, amid a period of "six simultaneous epidemics".

Diseases requiring treatment include polio, measles, and COVID.

Many doctors, nurses and cleaners have not been paid for four or five months and trees are being cut down in hospital courtyards to burn for heat, Dr Spiegel said.

"There's no question," he added, that the sanctions will kill more people than the Taliban.

Mr Brown said: "The first thing I want to see happen is the prime minister of Britain talks to the European Union and to Joe Biden, they arrange a pledging conference, get the money in, show that we can help people and save lives."

He continued: "It makes me angry to see that so little is being done. Babies die for many reasons but they should not be dying because of starvation and because they've frozen to death."

Sky News has approached the Foreign Office for comment.