Anyone arriving illegally in Britain will be prevented from staying, Prime Minister Rishi Sunak said in an interview published on Sunday, ahead of new legislation which is expected to be set out next week.
Under pressure from his own lawmakers to find a solution to the flow of migrants arriving in Britain across the channel from Europe, Sunak has made stopping small boats one of his five key priorities.
"Make no mistake, if you come here illegally, you will not be able to stay," Sunak told the Mail on Sunday newspaper.
Under current practice, asylum seekers who reach Britain are often able to remain in the country to have their case heard.
A new law to tackle the issue is due to be set out on Tuesday, the newspaper reported, after more than 45,000 people made the perilous crossing last year. Asylum applications to the United Kingdom are below the European Union average, official data shows.
Last year, former Prime Minister Boris Johnson agreed a deal to send tens of thousands of migrants, many having made the journey from Afghanistan, Syria or other countries suffering war, more than 4,000 miles away (6,400 kms) to Rwanda.
The policy has faced a legal battle after the first planned deportation flight was blocked by a last-minute injunction granted by the European Court of Human Rights. It was ruled lawful by London's High Court in December, but opponents are seeking to appeal that verdict.
Asked on Sky News whether those arriving in Britain illegally would be banned from claiming asylum, government minister Chris Heaton-Harris said: "I believe so, yes."
"Should people come to this country illegally then they will be returned or sent to somewhere like Rwanda."
The Mail on Sunday reported that under the new law asylum claims from those who arrive on small boats would be ruled inadmissible and they would be removed and permanently banned from returning.
"Our laws will be simple in their intention and practice - the only route to the UK will be a safe and legal route," interior minister Suella Braverman told the Sun on Sunday newspaper.
Heaton-Harris said he believed more safe and legal routes would be made available as part of the plan.