A vessel that will house up to 500 asylum seekers arrived in the UK on Tuesday after parliament passed its long-debated bill to curb migration.

The barge Bibby Stockholm was pulled by a tug into Portland harbor, off the Dorset coast in south west England, after the government’s controversial legislation overcame resistance in the House of Lords and was passed.

The vessel and the bill are both parts of prime minister Rishi Sunak’s strategy to stop migrants from making risky English Channel crossings in small boats. The legislation will become law after receiving the assent of King Charles III.

The Conservative government has pledged to “stop the boats” – overcrowded dinghies and other small craft that cross from northern France carrying migrants who hope to live in the UK. More than 45,000 people crossed the Channel to Britain in 2022; several died in the attempt.

The bill is intended to deter those journeys and will prevent migrants from claiming asylum in the UK. if they arrive illegally. Under the legislation, those caught will be sent back home or deported to another safe country and banned from ever re-entering the UK.

The government planned to send some of those who arrive without authorisation to Rwanda, but last month the Court of Appeal ruled it was illegal. The government is appealing the ruling to the Supreme Court.

Sunak cheered the passage of the bill but said the government must prevail at the higher court for the law to function properly.

“This is an important part of our work to stop the boats. Obviously it needs to be paired with the Rwanda partnership,” said Sunak’s spokesperson, Max Blain. “It’s right that we have this power in place so it can be utilised swiftly and we remain confident we will be successful in the challenge in the Supreme Court.”

The bill was approved after an all-night tussle on Monday between the House of Commons, where the governing Conservatives have a majority, and the unelected House of Lords, which can amend but not block legislation.

Elected MPs defeated amendments that would have included protections for modern slavery and child detention limits.

The United Nations human rights and refugee chiefs said the bill was at odds with Britain’s obligations under international law and will have “profound consequences” for people seeking protection.

The UN warned that the law would even deny protection to children with legitimate claims who are traveling without parents – some of whom might have survived human trafficking.

The Bibby Stockholm is expected to start housing people in two weeks. Its arrival on Tuesday at the port inspired two groups of protesters opposed to it.

Some locals are worried about the impact new arrivals will have on their town. A second group, Stand Up to Racism, said it welcomed refugees but objected to what it calls a “prison barge”.