The government is facing questions over whether the system at the heart of its plans for digital ID can be trusted to keep people's personal data secure.
Digital ID will be made available to all UK citizens and legal residents but will only be mandatory for employment, under the government's proposals.
Full details of how the system will work have yet to be announced but Prime Minister Sir Keir Starmer has insisted it "will have security at its core".
It will be based on two government-built systems - Gov.uk One Login and Gov.uk Wallet.
One Login is a single account for accessing public services online, which the government says more than 12 million people have already signed up to.
By this time next year that might be as many as 20 million, as people registering as company directors will have to verify their identity through One Login from 18 November.