Rishi Sunak’s plan to deport asylum seekers to Rwanda received its first parliamentary defeat on Monday after peers backed calls for protections to be introduced before any flights take off. The House of Lords voted for a motion that sought to delay ratification of the new Rwanda treaty until the government can show the country is safe. The vote on Monday night, by 214 votes to 171, was an unprecedented move seeking to pause implementation of the deal that paves the way for the asylum scheme. Under the terms of the safety of Rwanda bill, the law will not come into force until the treaty is ratified. The bill was passed by the Commons last week but it followed a Tory row that damaged the prime minister’s authority. Downing Street has insisted that flights to Rwanda will not be delayed by the Lords vote and had warned peers prior to the vote that a failure to pass the legislation would be an attack on the “will of the people”. Peers were debating a report from the House of Lords international agreements committee (IAC), which spearheaded the unprecedented move to delay the treaty. James Cleverly, the home secretary, signed the legally binding pact with Kigali in December, saying it addressed concerns raised by the supreme court about the possibility of asylum seekers deported to Rwanda then being transferred to a country where they could be at risk. But the cross-party Lords committee said promised safeguards in the treaty are “incomplete” and must be implemented before it can be endorsed. Labour peer, Lord Goldsmith, who chaired the committee, told the upper house that the report identified at least 10 issues where “significant additional legal and practical steps” must be implemented to ensure the safety of asylum seekers. He said: “We are not saying the treaty should never be ratified but we are saying that parliament should have the opportunity to scrutinise the treaty and its implementing measures in full before it makes a judgment that Rwanda is safe.” Conservative former cabinet minister, Lord Howell, criticised the “rather patronising tone one hears in some comments about Rwanda and its judiciary and legal system as though it could not possibly have high enough standards”. Pointing out the country has recently become a Commonwealth member, he said: “I can understand the Rwandan government’s exasperation and that of senior legal figures at the implication that their system somehow has got to be reinforced, made over and renewed to bring it up to scratch and be called safe.” But another Tory peer, Lord Balfe, said he could not think of “any country in Africa that I would wish to go and live in”. The motion received support from Labour and the Lib Dems, as well as crossbench peers and some on the “one nation” wing of the Conservative party. It is the first time that the Lords has approved a motion to delay ratification of an international treaty since legislation was introduced in 2010. Lord Sharpe of Epsom, the Home Office minister who responded to the debate, accused Labour peers of “using the House of Lords to frustrate our plans to stop the boats”. Downing Street has played down the significance of the vote. Speaking before the Lords motion, the prime minister’s spokesperson said it would not delay any flights for Rwanda. “My understanding is that if the motion was successful it would simply require the government to layer [the legislation] with an oral statement and wouldn’t impact on the timelines for getting flights off the ground,” they said. Baroness Shami Chakrabarti, the Labour peer and barrister, said the vote was a major blow to the government’s plan: “Mr Sunak’s dog whistle will be muted or at least delayed. Today’s debate has been crucial.” A Labour spokesperson said: “This is a cross-party amendment with support from across the House of Lords which simply asks the government to properly implement the standards and safeguards over the Rwanda treaty that they are in theory committed to. It is fundamentally untrue to say that this measure blocks anything, they should stop blaming everyone else for their chaos.” Leader of the Liberal Democrats in the House of Lords, Dick Newby, said: “Tonight has delivered yet another blow to Rishi Sunak and his failing Rwanda scheme. “From day one, this policy has been a totally unworkable waste of time and money. Yet the Conservatives are obsessed with pushing it forward, no matter what evidence arises to the contrary. “The government should now accept reality and move on from this white elephant of a policy.”