A Plaid Cymru Assembly Member has said she is prepared to go to jail rather than carry the proposed new ID card.
Wood: concern over costs and civil liberties
Plaid Cymru AM Leanne Wood AM has signed up to a campaign in protest at the UK Government plans.
Ms Wood, who speaks on social justice for her party, called ID cards "a very expensive Big Brother device".
The Labour government hopes ID cards will help fight illegal immigration, fraud, terrorism, organised crime, and identity theft from 2008.
The cards would be a way of checking the entitlement of an individual to receive services and benefits, including welfare payments and treatment under the NHS.
But there has been opposition to the plans, with some critics claiming the cards might cause friction among ethnic minority communities.
There are also fears that the cards would simply drive illegal immigrants into hiding, forcing them to avoid contact with hospitals and police.
Ms Wood said: "If, for some reason you get picked up by the police and you don't have your card or you've lost it, you could well end up behind bars."
Ms Wood, a former probation officer and lecturer in social work, said many people could end up going to prison.
She added: "I'm ready to go to prison if the government presses ahead with this dangerous plan. I do not believe that I should have to identify myself as a matter of course."
The Home Office said: "An identity cards scheme would help disrupt the use of false and multiple identities by organised criminals and those involved in terrorist activity; tackle illegal working and immigration abuse; enable easier and more convenient access to services and ensure free public services are only used by those entitled to them; and help protect people from identity fraud and theft.
"The current best estimate for the unit cost of an adult passport/ID card package for UK citizens valid for 10 years is £93 with the charge for a 'standalone' card estimated at £30.
"The actual amount charged to a person will depend on future policy decisions on charging within the scope allowed by the Identity Cards Bill."