The vivid display of disunity, nevertheless, has damaged Mr. Sunak’s authority. And it raised further questions about the effectiveness of the contentious legislation, which will now be considered by the House of Lords, the unelected upper chamber of Parliament, where more opposition is expected.

Under the Rwanda scheme, which has yet to be carried out, asylum seekers who arrive on the British coast in small, often unseaworthy, inflatable boats would be sent to Rwanda to have their claims heard there. But even if they were granted refugee status they would have to stay in the African country rather than settle in Britain.

The program has been condemned by human rights groups and refugee charities, and was ruled unlawful last year by Britain’s Supreme Court. The latest legislation is designed to redress the concerns raised by the court, although critics worry that the Rwanda policy could still be in breach of international law.

The Supreme Court ruled that it was not legal to send asylum seekers to Rwanda because there was a risk that they would be returned to their countries of origin, where they might be in jeopardy. The new legislation was designed to overcome that hurdle.