The database that will hold biometric information for all UK-based ID card and passport holders is up and running and already contains the details of 538 people, according to identity commissioner Joseph Pilling.

The National Identity Register will hold the biometric and biographical details of anyone who applies for an identity card or a biometric passport in a central database.

Cards and passports are not compulsory for UK citizens but are necessary if they want to travel overseas. Some 75,000 ID cards have already been issued.

Foreign nationals are compelled to carry ID cards. Their details have not yet been put on the register, but will be "in due course", the commissioner said.

Pilling, who took up the role of identity commissioner for 18 months in October, was giving evidence to the Home Affairs select committee for the first time.

He told the committee that he saw the primary purpose of his role as being to keep the public informed.

"It's my job to find out what's going on [in the scheme] and tell people about that," he said.

Pilling will have four full-time staff and a budget of £560,000 a year.

He insisted he had made his desire to be independent clear to the Home Secretary, Alan Johnson, and would not bend to political pressure.

"When I met the Home Secretary he said that he wanted me to be independently minded and I said I had every intention of being so," said Pilling.

Asked about the dangers of "function creep" – the possibility that cards could be used for a purpose other than that for which they were introduced - he said that he did not see it as a problem so long as the cards remained voluntary.

Pilling added he had written to the Identity and Passport Service for information about how it intends to share data collected under the scheme.

"My aim is to put that information into the public realm as fast as possible, allowing people to come to their own conclusions about whether it is reasonable or not," he said.