Almost 1,000 migrants arrived in the UK after crossing the Channel on Saturday, government figures show.
Long queues of people thought to be migrants could be seen waiting to be processed at the Border Force complex in Dover, Kent, as a total of 990 arrived.
Almost 40,000 have reached the UK so far this year after attempting the treacherous journey from France, crossing the world’s busiest shipping lanes in dinghies and other small craft, provisional figures show.
It is the highest number of arrivals in one day for several weeks, with most crossings taking place on Sunday mornings.
The highest number in a single day was set on August 22 when 1,295 people arrived in the country.
It comes after an immigration watchdog said it was left “speechless” by conditions at the Manston migrant processing center in Kent and warned the site is now past the point of being unsafe.
Borders and Immigration Chief Inspector David Neal told MPs earlier this week that Manston was supposed to accommodate between 1,000 and 1,600 people, but there were 2,800 at the site on Monday when he visited the site Monday, and that more arrived.
The revelations prompted the Refugee Council to call for “urgent” action and call for a meeting with ministers to discuss proposals to tackle the problems.
Migrants must stay at the short-term detention center, which opened in January, for 24 hours while undergoing screening before being transferred to immigration detention centers or asylum accommodation, currently hotels .
The Sunday Times reported that Home Secretary Suella Braverman has been accused of failing to act on legal advice received at least three weeks ago warning migrants were being detained for unlawfully long periods.
A Home Office spokesman said: “The Home Secretary has taken urgent decisions to alleviate the problems at Manston and find alternative accommodation. Claims that this was deliberately ignored are completely unfounded.
“It is right that we look at all available options so that decisions can be made based on the latest operational and legal advice.
“The number of people arriving in the UK on small boats has reached record levels, putting our asylum system under incredible pressure and costing the British taxpayer millions of pounds a day.”
Cabinet minister Michael Gove said the situation at Manston was “deeply concerning” but denied the Home Secretary was ignoring or dismissing legal advice.
“The situation in Manston is not what it should be,” he told Sky News’ Sophy Ridge On Sunday programme.
“Everyone recognizes it. At the moment we have more than 2,000 people there.”
The Liberal Democrats have called on the government to publish the legal advice that Ms Braverman reportedly ignored.