LONDON - Britain's government said on Friday that it would set out measures to limit courts' ability to block the deportation of illegal migrants, as part of changes to proposed legislation which will go before parliament next week.

Halting the flow of asylum seekers and other migrants who use small boats to cross the Channel from France is one of Prime Minister Rishi Sunak's top priorities for this year.

More than 45,000 such migrants landed on England's southern coast last year - up 500% in the last two years - and the government forecast on Wednesday that the number would rise to 56,000 this year.

"To speed up removals, amendments will make clear that the UK's domestic courts cannot apply any interim measure to stop someone being removed if they bring forward a legal challenge, aside from ... where they are at risk of serious and irreversible harm," Britain's interior ministry said in a statement.

Other changes to the law will allow undocumented migrants to be classed as adults if they refuse to undergo what the government described as "a scientific age assessment", and permit immigration officials to search migrants' mobile phones.

"The changes I am announcing today will help secure our borders and make it easier for us to remove people by preventing them from making last minute, bogus claims, while ensuring we strengthen our safe and legal routes," interior minister Suella Braverman said.

Charities supporting refugees say that Britain currently offers very limited options for most migrants to apply for asylum before entering the country, or to enter Britain legally with a view to making an asylum claim.

Britain's government is also seeking to discourage illegal immigrants by deporting them to Rwanda, regardless of their origin, but so far British courts have blocked this.

(Reporting by David Milliken)