British charities and officials are warning of increasingly dire conditions at a migrant processing center in England and urging Prime Minister Rishi Sunak to act.

The situation at the Manston asylum processing center constituted a “breach of humane conditions,” British Conservative lawmaker Roger Gale said Monday, as dozens of charities wrote to the prime minister to raise concerns about “overcrowding.”

The Manston migration center in Kent, southeast England, is currently holding around 4,000 people, among them women and children, despite being intended to hold only 1,500, local MP Gale told Sky News.

“That is wholly unacceptable,” Gale, who visited the former RAF base last week said, though he added staff were “trying to do a good job under impossible circumstances.”

It comes as dozens of charities signed an open letter from the charity Positive Action in Housing to Sunak, raising concerns about what they called “overcrowding and inhumane conditions” at the Manston center.

Charities urged British prime minister Rishi Sunak to take action over "inhumane conditions" at the Manston center. Gareth Fuller/PA Images/Getty Images

“We take the safety and welfare of those in our care extremely seriously and are working closely with our health professionals and the UK Health Security Agency to ensure their wellbeing,” the Home Office told CNN.

The Home Office also confirmed it was aware of a very small number of cases of diphtheria reported at the Manston center: “The Home Office provides 24/7 health facilities at Manston, including trained medical staff and a doctor.”

On Sunday, around 700 people who crossed the English Channel in small boats were relocated to Manston after “incendiary devices” were thrown at a migration center in Dover, local police confirmed.

Immigration Minister Robert Jenrick, who visited Manston on Sunday, acknowledged the “immense pressure” at the center in a tweet.

“Over 1,000 migrants crossing the Channel yesterday creates immense pressure. I was hugely impressed by the staff I met, managing this intolerable situation,” Jenrick said on Sunday.

The warnings come as criticism regarding the re-appointment of Suella Braverman as Home Secretary continues. Braverman is known for her tough stance on immigration.

More than a hundred refugee charities wrote an open letter to Braverman on Monday, urging her to address what they called a “backlog in asylum cases,” and to create safe routes for refugees to travel to Britain.

The letter referred to comments made by Braverman during the Conservative Party conference earlier in October, in which she said it would be her “dream” and “obsession” to see a front page of the Telegraph newspaper show a plane of migrants taking off to Rwanda, where some UK asylum seekers could be relocated under a controversial scheme.

“You have referred to this country’s proud history of offering sanctuary. So, we ask you to make this happen with a fair, kind and effective system for refugees,” the letter said.

Braverman – who has referred to illegal crossings of the English Channel as “an invasion” – defended her immigration policies on Monday.

Speaking to lawmakers at the House of Commons, she said she had tried to prepare the Manston site for a surge of people, and denied allegations that she blocked the use of hotels for immigrants.

“I foresaw the concerns at Manston in September and deployed additional resource and personnel to deliver a rapid increase in emergency accommodation,” she said.

“What I have refused to do is to prematurely release thousands of people into local communities without having anywhere for them to stay,” she added, saying that it will be the “worst thing to do.”