Britain on Wednesday announced plans to house around 500 asylum seekers on a barge, as the government seeks cost-cutting measures and deterrents for arrivals crossing the Channel.

Following his pledge to stop the small boats used by tens of thousands of migrants each year to make the treacherous trip, Conservative Prime Minister Rishi Sunak said the barge would save money and reduce pressure on hotels.

The Conservative government has already put forth a plan to outlaw asylum claims by all illegal arrivals and transfer them to "safe" third countries, such as Rwanda.

"We have to use alternative accommodation options, as our European neighbours are doing -- including the use of barges and ferries to save the British taxpayer money and to prevent the UK becoming a magnet for asylum shoppers in Europe," said Immigration Minister Robert Jenrick.

But charity group Refugee Council said the barge will be "completely inadequate" for "vulnerable people who have come to our country in search of safety having fled beatings and death threats in countries such as Afghanistan and Iran".

The barge that will be berthed in Portland Port is the first of its kind in the UK and will accommodate single men while their asylum claims are processed, with the first residents due in the "coming months".

"We can't have a situation (where) we are collectively spending £6 million a day on hotels for illegal asylum seekers," said Sunak.

"We're bringing forward alternative sites, like indeed the barge that we've announced today, that will save us money and indeed reduce pressure on hotels," he added.

The "Bibby Stockholm", which is to be operational for at least 18 months, will provide basic accommodation and healthcare, catering facilities and round-the-clock security.

It was previously used by the Netherlands and Germany to house asylum seekers.

- Increase in crossings -

Residents whose claims are refused and have exhausted their appeal rights will be removed from the country, said the government.

"We are keen to play our part in the national effort to house some of the thousands of people needing accommodation," said Bill Reeves, chief executive of Portland Port.

"We encourage everyone in the community to approach this with an open mind and help us show other areas just how successful this type of initiative can be, both for the migrants and the local community," he added.

The Home Office, which is exploring the use of further vessels, said the move "brings the UK in line with other countries around Europe", with the Netherlands also housing migrants on vessels.

Sunak has vowed to stop crossings of the Channel, which hit more than 45,000 last year.

He unveiled legislation last month to stop migrants illegally making the treacherous journey on small boats.

French authorities said they rescued 41 migrants stranded in the Channel in two separate missions on Wednesday, including three children suffering from hypothermia.

The British government last announced that surplus military sites will also be used to accommodate migrants who have entered the UK illegally.

Almost 88,000 people have made the crossing of one of the world's busiest waterways since 2018, leading the country's asylum system to become overloaded.

More than 160,000 people were awaiting an asylum decision as of the end of December 2022, with most having waited more than six months, according to official figures.