Tens of thousands of unauthorised migrants who seek sanctuary in the UK will be flown more than 4,000 miles to Rwanda under a new set of immigration policies, Boris Johnson has said. The prime minister insisted at a press conference that the African state, criticised last year by the UK for its human rights record, was one of the safest countries in the world. He also announced that the Royal Navy would take over patrolling the Channel to intercept small boats from France. Home Office insiders confirmed the plan was to give detainees a “one-way ticket” to the country and “encourage” them to establish new lives there. The home secretary, Priti Patel, visited the Rwandan capital, Kigali, on Thursday to sign what the two countries called an “economic development partnership”. The timing of the announcement has led to claims that Johnson is using the policy to deflect from becoming the first prime minister to be found guilty of a criminal charge while in office. Speaking at a press conference in Kent, Johnson said the scheme was needed to “save countless lives” from human trafficking by breaking the business model of traffickers. “The deal we have done [with Rwanda] is uncapped, and Rwanda will have the capacity to resettle tens of thousands of people in the years ahead. And let’s be clear, Rwanda is one of the safest countries in the world, globally recognised for its record of welcoming and integrating migrants,” he said. Asked about Rwanda’s poor human rights record – human rights groups have logged the torture of detainees – he said: “Rwanda has totally transformed. Over the last few decades it has totally transformed from what it was.” He said the Royal Navy would from Thursday take over “operational command” from Border Force in the Channel to ensure “no boat makes it to the UK undetected”. Johnson took aim at lawyers who might challenge the government’s proposals on behalf of recent arrivals. “If this country is seen as a soft touch for illegal migration by some of our partners, it is precisely because we have such a formidable army of politically motivated lawyers who for years have made it their business to thwart removals and frustrate the government,” he said. Johnson defended the cost of the Rwanda plan, which will include an initial payment of £120m, saying the asylum system was already costing £1.5bn a year and hotel costs would only increase. He said he wanted to make clear to people arriving on the Kent coast that they were better off taking legal routes, and the new plan would “over time prove a very considerable deterrent”. Asked about cost comparisons with putting people up in the Ritz, the prime minister said: “What’s happening already, the asylum system is already costing this country £1.5bn a year. The hotel costs are now £5m a day. You talk about the Ritz – they are now £5m a day, and it’s climbing. And unless we can beat the business model of the gangs, I’m afraid it will continue to climb.” It remains unclear whether only men will be sent to Rwanda; whether there will be a right of appeal; and whether cases will be initially processed in the UK, with only those deemed to be “economic migrants” removed from the country. It is anticipated that removals will initially be taken to a hostel in Kigali for processing. Hope House, in the Gasabo district of Kigali, is currently being used as accommodation for tourists, according to Rwandan government officials. The east African nation’s government is understood to be in negotiations to lease the property, which is privately owned, so that asylum seekers sent from the UK can stay there temporarily while their claims are processed. Last year 28,526 people are known to have crossed the Channel in small boats, up from 8,404 in 2020. Dozens have died attempting the crossing, including 27 people when a single boat capsized in November.