LONDON (AP) — British lawmakers on Wednesday approved a sweeping bill that will dramatically curb migrants’ ability to seek asylum in the UK, despite critics’ allegations that it breaks international law.

Members of the House of Commons voted by 289 to 230 to back the Illegal Migration Bill, which the Conservatives government says will deter tens of thousands of people from trying to reach the country in small boats across the English Channel each year.

It now goes to the House of Lords, where it faces strong opposition — though the unelected upper chamber of Parliament can only amend, not block, the legislation.

The large Conservative majority in the Commons ensured its passage there, despite opposition condemnation and claims legislators had not had enough time to scrutinise the legislation.

“This government has sought to railroad this deplorable, disgusting bill through the House of Commons,” said Stephen Flynn of the opposition Scottish National Party.

The legislation bars asylum claims by anyone who reaches the UK by unauthorised means, and compels the government to detain and then deport them “to their home country or a safe third country.” They would be banned from ever re-entering the UK.

Lawmakers rejected several opposition amendments that would have watered down the bill, including changes to exempt pregnant women and children from detention.

Immigration Minister Robert Jenrick said the bill is designed to send the message that “if you enter the United Kingdom illegally, you will not be able to build a life here.”

Critics say the plan is unethical and unworkable. They say people fleeing war and persecution can’t be sent home, and a UK plan to deport asylum-seekers to Rwanda is mired in legal challenges, so migrants are set to languish in UK detention with no way out.

The bill also bars migrants who are victims of human trafficking from using Britain’s modern slavery laws to prevent deportation. That has angered former Prime Minister Theresa May, a Conservative, who championed laws to protect trafficking victims when she was in office.

May said the bill was “a slap in the face to those of us who actually care about the victims of modern slavery” and would make victims’ plight worse.

The United Nations’ refugee agency has said the bill is a “clear breach” of the international Refugee Convention. The British government has conceded there is a strong chance it breaches the UK’s international refugee and human rights obligations, but is determined to fight legal challenges.

Britain receives fewer asylum-seekers than European nations such as Italy, Germany or France. But thousands of migrants from around the world travel to northern France each year in hope of reaching the UK across the Channel.

More than 45,000 people arrived in Britain in dinghies and other small boats in 2022, up from 8,500 in 2020.