By Andrew MacAskill

LONDON (Reuters) -The number of migrants arriving in Britain in small boats hit a record for a single day on Monday, as the rise in dangerous journeys across the English Channel continues despite UK government plans to deport those arriving illegally to Rwanda.

Britain’s Ministry of Defence said 1,295 people in 27 boats were intercepted after making the crossing from the European mainland on Monday. The figure surpasses the previous daily record of 1,185 set last November.

The summer surge happens most years, but is now larger than normal as alternative routes have been shut down. The rate of arrivals in the first eight months of this year is almost double that during the same period last year.

The outgoing Prime Minister Boris Johnson had hoped that the threat of deporting people to Rwanda announced in April alongside other efforts, such as handing the navy the responsibility for intercepting migrants, would act as a deterrent to those arriving in dinghies and small boats.

Britain’s Refugee Council said the figures were “yet more evidence if needed that the government’s cruel Rwanda removals plan – supposedly a deterrent to dangerous Channel crossings – simply isn’t working.

Under an agreement struck in April, Britain will send tens of thousands of migrants who arrive on its shores illegally more than 4,000 miles (6,4000 km) to the East African country.

The policy will be the subject of a legal challenge in London’s High Court in early September when a coalition of human rights groups and a trade union will argue that the Rwanda policy is unworkable and unethical.

The first planned deportation flight in June was blocked by a last-minute injunction from the European Court of Human Rights.

In 2021, 28,526 people were detected arriving on small boats – with the highest number from Iran followed by Iraq, Eritrea, and Syria. So far this year, more than 22,000 migrants have come to Britain, with government officials warning 60,000 could arrive by the end of the year.

At least 166 people had died or gone missing making the crossing since 2014.

A report by parliament’s cross-party home affairs committee said last month that the rise in crossings may be because of “scaremongering” by people traffickers that new rules are coming in and they are being pressured to travel now.

The recent rise in crossings was “unacceptable,” the UK government said. Not only are they an overt abuse of our immigration laws but they risk the lives of vulnerable people, who are being exploited by ruthless criminal gangs,” a spokesperson said.

Both candidates vying to replace Johnson as prime minister, Liz Truss and Rishi Sunak, have promised to push ahead with deportations to Rwanda.

(Reporting by Andrew MacAskill; Editing by Michael Holden and Mike Harrison)