Home Office contractors have been disciplined after trying to sell illegal drugs to asylum seekers at the crisis-hit processing centre at Manston in Kent. It is understood the issue came to light after asylum seekers at the site in Ramsgate complained that security staff had tried to sell them cannabis. Security guards also raised concerns that their colleagues were smoking the drug while on duty. A Home Office statement said: “The Home Office expects the highest standards of professionalism from all those contracted to manage the detention estate. The individuals involved in this incident were swiftly removed from the site and we will continue to take robust action against those whose behaviour falls beneath those high standards.” Labour said the latest revelation about the troubled site was evidence that the home secretary, Suella Braverman, “has completely lost control of the asylum system”. Braverman is facing a legal challenge over the conditions at Manston, which is housing thousands of people seeking refuge in the UK. On Thursday, the home secretary flew into Manston in a Chinook helicopter to visit the centre for the first time. The Home Office said more than 1,200 people had been moved off-site within the past four days. At one point, 4,100 people including children and pregnant women were living in a space designed for 1,600. The Guardian has revealed various infectious conditions on the site including diphtheria, scabies and MRSA. Chairs of several parliamentary select committees including the home affairs committee wrote to the home secretary on Wednesday raising concerns about conditions on the Manston site. These include lack of adequate safeguards for children on the site and a failure to identify which adults on the site should be designated “adults at risk” because of certain vulnerabilities. Stephen Kinnock, the shadow immigration minister, condemned the revelations. “The home secretary has completely lost control of an asylum system which has been broken by 12 years of Tory neglect and, as the prime minister has been forced to admit, isn’t processing claims fast enough. “This latest shocking revelation illustrates the extent to which the home secretary’s chaotic approach is putting children at risk. Labour has a plan to speed up the processing of asylum claims which has fallen by half since 2015 and to clear the backlog which is becoming a key recruiting tool for the criminal gangs. We would also invest in an elite specialist unit in the National Crime Agency to crack down on the criminal smuggler gangs.” Enver Solomon, the chief executive of the Refugee Council said: “This is appalling and yet further evidence that Manston is unfit for purpose with men, women and children subject to inhumane treatment.” Clare Moseley, the founder of the charity Care4Calais, which works with asylum seekers both in northern France and in the UK, said: “The Home Office pays outsourced contractors vast sums of money to take care of asylum seekers, but this does not remove their responsibility. This is a huge failure in oversight and care and the ultimate responsibility rests with Suella Braverman who needs to understand that she has a responsibility on behalf of our nation for the care of these incredibly vulnerable people.” Home Office sources said: “The Home Office takes the safety and welfare of detained persons in its care extremely seriously. Whistleblowing procedures are in place to enable service providers and Home Office staff to safely and securely report any concerns, including concerns of misconduct and inappropriate behaviours.”