Suella Braverman has been warned by council chiefs that Kent is at “breaking point” as a result of the migrant crisis, with the potential for disorder at an overcrowded processing facility and the risk of far-right violence.

In the letter to the Home Secretary, the leaders of 14 authorities including Kent County Council and Medway called on the Government to stop using the county as an “easy fix for what is a national, strategic issue,” claiming they were under disproportionate pressure because of their location.

“The situation at Manston is critical,” the local authority chiefs said, with tension among the detainees and outbreaks of diseases including coronavirus, scabies and diphtheria.

“We now have approaching 4,000 service users contained within segregated marquees as we approach the coldest months of the year, some having been on roll mats for over a month.”

There are “reports of tensions growing and concern about the potential for disorder”.

As the facilities become “more high profile”, incidents of “far-right activity continue to grow as these sites become a focus for local, regional and national attention, the council chiefs said.

They added that they were “deeply concerned about the potential for a further outbreak of disorder” after the firebombing of another immigration facility in Dover on Sunday.

The letter also said: “Secondary schools in Canterbury and Ashford currently have no year 7 and year 9 places for local children due to the unexpected and therefore unplanned for arrivals of refugee children disproportionately placed by the Home Office in these two local authority areas.”

At the same time Thanet councillors said residents appear to be mainly concerned with the apparent poor treatment of migrants on their doorstep.

Labour councillor Heather Keen said: “The unfortunate thing is it’s not something we can do much about locally, this is a national Government responsibility, it’s MoD (Ministry of Defence) land, and therefore our hands are tied, we just see this happening and it’s not good enough.

Fellow Labour councillor Steve Albon described Manston as a “deprived area” where the council struggles to provide residents who can no longer afford to pay their rent with emergency housing, adding that people were also concerned about the impact on local hospital admissions.

“We can’t cope with the extra pressure,” he added.

Thanet District Council said it had “no jurisdiction” over the site, which it previously raised concerns about with then home secretary Priti Patel.

“The council is aware of the growing number of reports relating to the site and will again be writing to the Home Secretary to express our concerns,” the council said.

Several Conservative councillors contacted by PA indicated the Government had instructed them not to talk about Manston.

A Home Office spokeswoman said: “The number of people arriving in the UK who seek asylum and require accommodation has reached record levels, placing unprecedented pressures on the asylum system.

“The Government is working with all local authorities in England, Wales and Scotland to provide more suitable accommodation for asylum seekers and to end the unacceptable use of hotels, with more than £21 million in grant funding already been provided to local authorities to help them respond to challenges in their area.”