The government has begun to advertise for an independent commissioner to oversee the £4.7bn National Identity Scheme.

The post is being advertised in The Sunday Times, and is intended to reassure the public that the scheme will not be subject to function creep and impinge further on civil liberties.

Home secretary Jacqui Smith said the commissioner will be formally independent and have a high public profile as a defendant of citizens' interests.

"I understand that people want strong oversight of the National Identity Scheme and I agree that the security or integrity of the scheme should never be taken for granted," she said.

The commissioner will scrutinise the way the scheme is implemented and managed, how information is stored on the national identity register and how identity cards are used in the public and private sectors.

The government began issuing the cards to foreign nationals in November.

By the end of the year they will be issued to people working in sensitive roles such as airside workers in airports. From 2010, cards will be issued on a voluntary basis to young people, though the Conservatives have vowed to scrap the scheme should they win the next General Election.