The government wants to relocate thousands of asylum seekers who arrive in Britain on small, inflatable boats each year to live in Rwanda, but legal challenges have so far prevented anyone being sent to the East African country yet.

The legislation is central to Sunak's pledge to stop the arrival of asylum seekers and he hopes the deportation flights will reverse the fortunes of his Conservative Party, which is heavily trailing in the polls with the next election looming.

Unelected members of the House of Lords, largely made up of former politicians and government officials, voted on Wednesday for a second time to amend the legislation to put more safeguards in place to protect the rights of asylum seekers.

The Lords voted for amendments that would require ministers to take "due regard to domestic and international law" and another that would only declare Rwanda a safe country when a treaty with Britain had been implemented.

The defeats for the government means the bill will be sent back to the House of Commons in a process known as "parliamentary ping-pong" where the two chambers try to find common ground.

The resulting back-and-forth means the bill is unlikely to become law until after parliament returns from its Easter break - in the middle of next month at the earliest.

This is likely to push back when the first deportation flights take off because, one government official said, it will probably take at least a month to organise them from the moment when the legislation passed.

The government suffered a setback to its plan to send asylum seekers to Rwanda last year when the UK's Supreme Court ruled the policy was unlawful because there was risk that people sent there could be sent back to their country of origin and their safety jeopardised.

To overcome objections by the court, Sunak's government is passing the bill that declares Rwanda a safe country for asylum seekers and disapplies parts of human rights law in an attempt to block further legal challenges.