Home Office contractors were told about traces of Legionella bacteria found on the Bibby Stockholm barge on the same day asylum seekers were transferred on to the vessel, Dorset Council has said.
The discovery eventually led to the removal on Friday of all 39 people who had boarded the floating accommodation docked in Portland on Monday.
The council has now said it informed the “responsible organisations”, barge operators CTM and Landry & Kling, about the preliminary test results on Monday, the same day it received them.
A Home Office official was then told about the discovery on Tuesday, the council said, but it is understood ministers did not know about the presence of the bacteria until Thursday.
A spokesperson said: “To be clear, it was not Dorset Council’s responsibility to inform the Home Office – that responsibility sat with CTM and Landry & King, the companies contracted by the Home Office to operate the barge.”
The Home Office did not comment on the statement, first reported by The Telegraph. CTM and Landry & Kling have also been contacted for comment.
The UK Health and Security Agency (UKHSA) was alerted on Wednesday evening to concerns about potential health risks and guidance was sought by the council.
The full timeline remains unclear and the council has not yet said whether it told contractors before or after the transfer of migrants on to the barge.
Immigration minister Robert Jenrick was understood to have told the operaters that they need to be more transparent in future.
It comes after 509 more people crossed the English Channel in 10 boats on Saturday, with one journey resulting in the deaths of six people when a vessel sank off the coast of France.
A Cabinet minister defended the Government’s immigration strategy on Sunday amid renewed pressure, including from Tory MPs, over its “stop the boats” pledge following the fatal incident.
At least six people died and at least 58 – many of them Afghans – were rescued after a boat got into difficulty off the coast of Sangatte on Saturday.
According to the accounts of survivors, around 65 people had originally boarded the overloaded vessel before a passing ship saw it sinking and raised the alarm at around 4.20am.
Wales Secretary David TC Davis admitted the crossings would “continue to be a problem”, but insisted some boats were being stopped.
“We have stopped a lot,” he told Sky News.
Rishi Sunak has made tackling the crossings one of five key priorities for his leadership and asked people to judge him on his management of the problem.
MPs have called for action against criminal people-smuggling gangs profiting from the journeys while campaigners have said the deaths were a preventable tragedy.
Home Secretary Suella Braverman described the incident as a “tragic loss of life” and said she had chaired a meeting with Border Force officials later on Saturday.
The Government was accused of allowing its “small boats week” of linked announcements on immigration to descend into farce following the Bibby Stockholm evacuation.
Senior Conservative backbencher David Davis said the “startling incompetence” of the Home Office had been laid bare after the evacuation.
However, ministers intend to push on with plans to hire more barges to house asylum seekers, as well as student halls and former office blocks, The Telegraph reported.
The people who had been on the Bibby Stockholm, which had been billed as a cheaper alternative to expensive hotels for those awaiting the outcome of their claims, are now back being housed in other accommodation.
The Home Office has said the health and welfare of asylum seekers “remains of the utmost priority” and that the evacuation took place as a precautionary measure, with all protocol and advice followed.
Mr Davies on Sunday defended the Government’s handling of the setback, saying its evacuations from the vessel “actually demonstrates how we’re putting the safety of people first”.
Asked whether the incident points to a wider failure within the Home Office, he told Times Radio: “No, it doesn’t. It doesn’t at all. The checks were being made.”
But shadow education secretary Bridget Phillipson said a “better, fairer system” is needed to tackle the backlog of asylum applications and cut the need for temporary accommodation.
She told the same programme that prosecutions of people smugglers are “falling” under the current Government.
Conservative MP Tim Loughton said the Government’s “small boats week” of linked announcements on immigration was a “hostage to fortune”.
He told Times Radio: “I think it was probably not a good idea to have a small boats week. It was a hostage to fortune and clearly it depends on how many people are risking their lives coming across the Channel, which is dependent on the weather and how people smugglers are operating.”