The borders watchdog said he was left speechless by “wretched conditions” during a visit to a migrant processing centre at Manston, which has already passed the point of being unsafe.
The independent chief inspector of borders and immigration, David Neal, was also concerned after discovering some of those guarding people on the site are not specifically qualified to do so.
He said that following his visit to the Ramsgate site on Monday he urgently raised this issue with the home secretary and the chief inspector of prisons, Charlie Taylor.
Migrants are meant to be held at the short-term holding facility, which opened in January, for 24 hours while they undergo checks before being moved into immigration detention centres or asylum accommodation – currently hotels.
Mitie Care & Custody manages Manston and it has specially trained detention custody officers on the site who are accredited by the Home Office. However, there are also private security staff on site who do not have the same specialist training.
Neal told an evidence session of the home affairs select committee that along with his concerns about some of those staffing the site he had spoken to a family from Afghanistan living in a marquee for 32 days and two families from Iraq and Syria living in the tented accommodation for two weeks sleeping on kit mats with blankets.
“This is pretty wretched conditions,” he said.
The Home Office could be facing hundreds of unlawful detention claims because many people are being held unlawfully for longer than the five-day time limit.
Committee member Stuart McDonald MP said: “It seems to have descended into a state of absolute chaos and disaster.”
Officials said that as the year went on it became increasingly difficult to move people out.
They confirmed that about 3,000 people are being held there on a site designed for 1,000 with a maximum of 1,600. This number is larger than any prison or immigration detention facility in the UK.
At the time of Neal’s visit there were 2,800 people at Manston and 190 at nearby Western Jetfoil with 24 en route from Western Jetfoil to Manston.
He said: “The numbers that have been described are clearly outstripping the capacity of the site.”
The lack of officers and guards to match the number of people was “sufficiently alarming” he said, adding: “When I discovered that I was frankly speechless and I’m not someone who is normally speechless.”
He said the situation at Manston showed a “creeping lack of ambition from the Home Office”.
“It’s a really dangerous situation. It’s failing to address vulnerability,” he said, adding that there were risks in terms of fire, disorder and infection on the site.
He said that, as revealed by the Guardian, cases of diphtheria had been confirmed but officials did not provide specific detail about any testing carried out to check whether there were any more cases than the four cases of which Neal had been informed.
Home Office officials told the committee there was 24/7 medical care available on the site and that they were trying to move people out of Manston as quickly as possible.