The Lord Chancellor has said ID cards should be made compulsory if introduced in the UK.
Lord Falconer said the final decision rests with Parliament
Lord Falconer told the BBC that the only way to get full benefit from the scheme was for people without a passport to carry one.
Prime Minister Tony Blair has said the government backs ID cards and fears over civil liberties are "misplaced".
Tory leader David Cameron criticised the cost, citing a report which puts the price at £19bn over 10 years.
Plans for ID cards have been rejected by the Lords, who want to know how much the project would cost.
Lord Falconer told BBC Radio Four's Any Questions: "The question is should you require - and I think ultimately, unless there is compulsion, you won't get the benefits of an ID card system - is it right to compel those that don't have a passport also to get an ID card?
"I think it is, I think it will become inevitable that you need reliable means of identification, both to stop people stealing your identity, and also making it much, much easier for you to deal with the state.
"You won't every time you want to change something have to fill in a long form, life will just become much easier."
The lord chancellor said the final decision would rest with Parliament and he added: "I think the government takes the view that to get the full benefits they will ultimately have to become compulsory."
'Monument to failure'
Mr Cameron has told Parliament that plans to introduce identity cards risk ending up as a "monument to the failure of big government".
He cited a report by the London School of Economics, which claims the scheme would cost between £10bn and £19bn over 10 years if the government followed its original plans.
Mr Blair said that report was drawn up by someone who was a campaigner against ID cards on civil liberty grounds.
The Home Office estimates the scheme will cost about £584m to run each year, with each combined biometric passport and identity card costing £93.