The government has revealed that tens of thousands of businesses will be accredited to make identity checks on customers and employees, should ID cards be introduced as planned in 2007.
Documents released by the Home Office last week predicted that 44,000 businesses and 256 government bodies would be given rights to check individuals' details against a national population database.
Officials conceded, however, that the figure was probably a "significant underestimate" and that in practice many more firms would be licensed to use ID cards to verify identities.
"We do not have a definitive list of applications but there are numerous situations were individuals are required to prove their IDs; for example, in banks, doctors' surgeries, retailers for proof of age, and any situation where you would be required to prove who your are," said a Home Office spokeswoman.
The Home Office revealed this week that it would not make it compulsory for employers to carry out biometric checks on staff to verify their eligibility to work, and it would not charge businesses to make the checks.
The news will be welcomed by smaller firms, for whom the biometric readers could prove expensive. According to initial Home Office estimates, readers could cost between £250 and £750.
Instead, Home Office officials are considering introducing a mobile phone-based system that would allow small businesses to verify that ID cards are genuine by texting the card details to the ID database and asking the card holder to type in a Pin.
However, the strategy has been questioned by some commentators, who suggested it weakened the government's claims that ID cards would stop illegal working.
"A Pin is not secure. If people are trying to get work illegally, they can easily pass the same card around if they look vaguely like the photograph. I am not sure it is fit for purpose," said cross-bench peer Lord Errol.
David Lacey, director of security at the Post Office and chairman of the ID cards private sector working group, said that in practice many businesses would choose to verify identities of staff and customers by checking Pins in a card reader rather than taking fingerprints or iris scans.
"There are different levels of use of the verification. It will cost more, take longer and you would have to be accredited to a higher level of security to do the maximum level of checks," he said.
The Post Office has a network of 30,000 card readers, which could be used to make simple checks on the authenticity of an ID card without resorting to biometrics, and retailers could do the same, said Lacey.
But businesses might choose to take biometric readings of staff employed in sensitive roles, for example, in finance or defence industries, he said.
Members of the private sector ID cards working group, which include Royal Bank of Scotland, HSBC and Royal Mail, are evaluating how ID cards could help businesses.
However, Lacey said, "This is still a long way off for businesses. It is way beyond their business planning. All we can do is look at this as something that has potential, is coming our way and we think is inevitable."
ID card contracts to be split into work programmes
Application enrolment and maintenance services
Will allow people to apply for ID cards and enrol their biometrics through a national network of enrolment centres and mobile units. Will cater for 10 million enrolments per year.
National identity register
Provision of datacentre service, hosting services, verification services and secure access services. Database will hold 100 million registration records.
Services to validate authenticity of ID cards, and in exceptional circumstances establishing an identity by searching the biometric database. Includes provision of secure network, a unit to sell ID services to businesses. It is predicted there will be 163 million identity transactions year.
Services to support procurement of systems, in-house operations, outsourcing of services, and shared services. Includes human resources, finance and procurement support, administration IT services, business administration services, legal and policy, security and fraud services.