Suella Braverman said small boat crossings will “fall dramatically” under her asylum plans as she insisted they are legal, but could not say when removals will begin.
The Home Secretary was also unable to set out when new detention centres for migrants will be built but said it will be “very clear” by the next election whether her scheme has been a success.
The backlash to plans to prevent anyone who arrives in the UK by unauthorised means from returning has been sharp, with the UN’s refugee agency calling it effectively an “asylum ban”.
Braced for legal challenges to the Illegal Migration Bill which he believes is key to his electoral chances, Prime Minister Rishi Sunak accused Labour leader Sir Keir Starmer of being “just another leftie lawyer standing in our way”.
But many questions remain over how successful how the policy will be, particularly with the Government’s controversial policy to forcibly remove asylum seekers to Rwanda grounded by the courts.
Ms Braverman told the BBC: “We will see, based on other countries’ experiences, that, once we’re able to relocate people who’ve come here illegally from the United Kingdom to another safe country, like Rwanda, or back to their own home country, then, actually, the numbers of people making the journey in the first place will fall dramatically.”
The Home Secretary claimed it was a “possibility” that up to 80,000 people could cross the Channel on small boats this year.
But she was unable to say when new detention centres would be built, or when the first removals would take place under the plans.
Ms Braverman told Sky News “we are rolling out new detention spaces”, but said “I’m not going to give precise dates” because “we’ve got logistical challenges that we’re always overcoming”.
“But very, very soon we will be expanding our detention capacity to meet the need,” the Home Secretary said.
On removals, she said: “I can’t give you precise dates, we have lots of processes which are in train.”
In a letter to MPs, Ms Braverman has conceded there is a “more (than) 50 per cent chance” her legislation may not be compatible with the European Convention on Human Rights (ECHR).
But she told Sky: “We’re not breaking the law and no Government representative has said that we’re breaking the law.
“In fact, we’ve made it very clear that we believe we’re in compliance with all of our international obligations, for example the Refugee Convention, the European Convention on Human Rights, other conventions to which we are subject.”
Ministers have not set a timeline for their mission of “stopping the boats” to be a success.
Ms Braverman told BBC Radio 4’s Today: “I think it will be very clear by the time of the next election whether we have succeeded or not.”
She also defended her disputed claim to MPs that “there are 100 million people around the world who could qualify for protection under our current laws” and “they are coming here”.
Asked about her comments on the BBC, the Home Secretary said: “I see my role as being honest … I’m not going to shy away from displaying the enormity of the problem that we are facing.
“The UN itself has confirmed there are over 100 million people who are displaced globally, because of all sorts of factors like conflict or persecution … and these are many people who would like to come to the United Kingdom.”
During a feisty exchange at Prime Minister’s Questions, Mr Sunak was also unable to say when he would meet his pledge to “stop the boats” and instead tried to implicate the Labour leader.
Sir Keir, a former director of public prosecutions, said the Prime Minister should be “apologising, not gloating” over the increasing numbers of small boat crossings.
Mr Sunak responded: “Stopping the boats is not just my priority, it is the people’s priority, but his position on this is clear.
“He wanted to, in his words, scrap the Rwanda deal, he voted against measures to deport foreign criminals and he even argued against deportation flights.
“We know why, because on this matter he talked about his legal background, he’s just another leftie lawyer standing in our way.”
The plans announced on Tuesday would see migrants who arrive through unauthorised means deported and hit with a lifetime ban from returning.
Anyone who crosses the Channel in a small boat would only be eligible for asylum in a “safe” third country, such as Rwanda.
Powers would be granted to detain migrants for 28 days without recourse for bail or judicial review, and then indefinitely for as long as there is a “reasonable prospect” of removal.
The UN’s refugee agency, the UNHCR, said it was “profoundly concerned” by the Bill and urged Parliament to reject it. If passed, it will amount to an “asylum ban”, the group said.
Labour described the policy as a “con” that was no more likely to succeed than the Conservative’s previous efforts.
In 2022, a record 45,755 migrants arrived in the UK after crossing the Channel.
More than 3,000 have already made the journey this year. Home Office figures show 197 made the crossing on Monday – the first arrivals since February 24 – taking the total to date to 3,150.
Related: Unhinged or unworkable? The Tory’s Illegal Immigration Bill is both
