Rishi Sunak has said he is confident Home Office staff will enact the Rwanda deportation scheme, despite fears that could put them in breach of international law. The FDA, the union for senior civil servants, has threatened ministers with legal action if they are forced to implement the government’s Rwanda deportation bill despite legal concerns. The union has warned civil servants could be in violation of the civil service code, and potentially open to prosecution, if they followed a minister’s demands to ignore an urgent injunction from Strasbourg banning a deportation. The FDA sent a pre-action legal letter to James Cleverly, the home secretary, outlining its concerns last month. It is considering a potential challenge to the government over whether officials implementing the bill could be in breach of international law and therefore the civil service code. The union is examining the option of launching a judicial review. Speaking on a flight to Poland, Sunak said: “I’m clearly and firmly of the view that civil servants know that what they’re there to do is support the government and that’s what I’m confident they will do in this instance. “That’s why we specifically changed the civil service [guidance], which is one of the steps that we made a little while ago, to make it crystal clear that when it comes to rule 39 decisions, the bill gives ministers the discretion to decide what to do about those.” He added: “I wouldn’t have put that power in there if I wasn’t prepared to use it, but our changes to the code make it crystal clear that civil servants will be expected to follow ministerial guidance on that point when we get there, or if we get there.” The prime minister said this week that preparations were under way for the first deportation flight to take off in July, after the government’s Rwanda deportation bill passed on Monday night. The Rwanda bill is expected to become law on Tuesday after the conclusion of a marathon “ping pong” battle, in which the Commons and Lords passed it back and forth before peers backed down over their amendments. Five people including a child died while attempting to cross the Channel on Tuesday, hours after the bill cleared parliament. Cleverly, the home secretary, said “these tragedies have to stop” and that ministers were doing everything they could to stop the boats. The developments open the way for legal battles over the planned deportation of dozens of people seeking asylum in the UK. Michael Tomlinson, the illegal migration minister, conceded that victims of torture could be deported under the scheme. He told the BBC Radio 4 Today programme: “Rwanda is a safe country and yes, it will be possible to remove those to Rwanda.” Asked about victims of trafficking, Tomlinson repeated: “Rwanda’s a safe country … You could ask me an infinite number of challenges, you could say here’s a handbook … You’re not going to get that clarity because the act hasn’t yet come into force.” He added that there were “likely to be legal challenges” regardless of what the government said. Yvette Cooper, the shadow home secretary, called the scheme an “extortionately expensive gimmick” and said that if Labour won the general election, it would introduce an alternative. “This is not a serious plan to actually tackle the problem,” she told BBC Breakfast. “It’s costing around half a billion pounds for just 300 people to be sent to Rwanda, that’s less than 1% of asylum seekers. It’s not addressing the 99%, it’s not addressing the overall problem. “That’s why Labour would replace the Rwanda scheme with a new plan to boost our border security, to go after the criminal gangs and their networks right across Europe,” she said. “We’d also have stronger powers, stronger intelligence agreements, and new fast-track systems in the UK, so that we have a new returns and enforcement unit.”