Home secretary Priti Patel branded the actions of asylum seekers being housed at a former military barracks in Kent on Friday as “appalling” and “deeply offensive” after fire broke out during a protest over conditions at the site, where hundreds have contracted coronavirus.

The fire followed days of protests over conditions at Napier Barracks near Folkestone, which the Home Office has started using to accommodate some asylum seekers in preference to the usual system of housing them in hotels or flats. Residents have complained that dormitories in the disused military facility are overcrowded, allowing coronavirus to spread.

The home secretary’s statement drew criticism from groups working with asylum seekers.

Bella Sankey, director of Detention Action, which represents people in immigration detention, questioned why Ms Patel had made the fire a political issue. “Her divisive, inflammatory and knee-jerk response will only fan the flames of prejudice and undermine the rule of law,” Ms Sankey said.

The fire broke out during a protest by asylum seekers who, according to the Home Office, were objecting to not being moved off the site during the coronavirus outbreak.

Kent Fire and Rescue said they had been called shortly before 3pm and had sent eight vehicles. Footage on social media showed flames billowing from one of the Nissen huts where the asylum seekers have been housed. The brigade said on Friday evening that the blaze was under control.

Kent Police, who were also called, said they were investigating and that the fire, which they said had caused “considerable damage” to one part of the site, was thought to have been started deliberately. However, no arrests has so far been made and no serious injuries had been reported.

Ms Patel said action such as that by the asylum seekers would not be tolerated and the Home Office would support “robust action” by the police against anyone vandalising property or threatening staff.

“The damage and destruction at Napier barracks is not only appalling but deeply offensive to the taxpayers of this country who are providing this accommodation while asylum claims are being processed,” Ms Patel said.

Organisations and people including Rosie Duffield, MP for the nearby constituency of Canterbury, and the bishop of Dover, Rose Hudson-Wilkin, wrote to Ms Patel on Thursday demanding the immediate end to using the barracks for asylum seekers.

Until recently, around 400 people who had claimed refugee status after arriving on small boats across the English Channel had been housed there. There have been reports that some dormitories housed up to 28 people with limited shower and lavatory facilities, making self-isolation impossible.

Campaigners believe the Home Office has shifted to using the spartan barracks to house people awaiting processing of asylum claims after facing criticism for putting some up in empty hotels. People awaiting processing of asylum claims are not detainees and are usually placed in normal housing.

The home secretary attracted ridicule in October after it emerged her department had considered a series of outlandish proposals to deter asylum seekers from crossing the Channel in small boats, including floating walls and a wave machine to drive boats back into French waters.

Ms Patel on Friday dismissed the idea that the accommodation at the barracks was inadequate. “This site has previously accommodated our brave soldiers and army personnel,” she said. “It is an insult to say that it is not good enough for these individuals.”