Britain on Friday said it would introduce a mandatory digital ID scheme for British citizens and residents starting a new job as a measure to deter illegal immigration.

"It will make it tougher to work illegally in this country, making our borders more secure," Prime Minister Keir Starmer said in a statement announcing the move, which had been previously reported.

Polling shows immigration is top of voters' concerns in Britain, with Starmer under intense pressure to stop migrants entering the country illegally by making crossings in small boats from France.

The plans, which the government had previously said it was considering, drew criticism from political opponents who say it would not deter migrants and could infringe on civil liberties.

The government said the digital ID would be held on people's mobile phones and would become a mandatory part of checks that employers already have to make when hiring a worker.

It would, in time, also be used to provide access to other services like childcare, welfare and access to tax records.

In the 2000s, Starmer's Labour Party, then led by Tony Blair, attempted to introduce an identity card, but the plan was eventually dropped by Blair's successor, Gordon Brown, amid opposition by critics who called it an infringement of civil liberties.

Britons have not been issued with identity cards since their abolition after World War II, and typically use other official documents such as passports and driving licences to prove their identity when required. (Reuters)