Biometric scans include iris images, face dimensions and fingerprints
Trials of ID cards have revealed problems with the scanning systems central to the project, it has emerged.
"Biometrics" such as fingerprints, iris images or face scans will be used for the cards but the trials found that not all people could use all the systems.
It was harder to scan the irises of black people and over-59s.
And some fingerprint scanners did not work with large fingers. Ministers say they were only "teething" problems and the technology is on track.
Some experts argue the technology may never be good enough.
Professor Angela Sasse, a biometrics expert who has advised MPs on the home affairs select committee, said biometric technologies were "a lot less mature" than manufacturers made out.
"To be honest, I think it is a possibility that eventually we will conclude it isn't good enough or that the current systems we're using aren't good enough for a large scale public domain application such as an ID card," she said.
The trials involved 10,000 volunteers, although the detailed research centred on 2,000 "quota" people chosen to match the general population and 750 disabled people.
It took an average of 7 minutes 56 seconds for the "quota" group to be enrolled for a card through biometric scans.
For disabled people, the process took an average of 8 minutes and 15 seconds.
Most of the volunteers were able to be scanned for iris images, facial dimensions or fingerprints.
But 0.62% of the disabled group could not enrol using any of the systems.
There were greater problems in checking people who had already been given cards - a process which took between 39 seconds and one minute 20 seconds.
Facial scans worked for 69% of the "quota" group and 48% of disabled volunteers.
Fingerprints worked for 81% of "quota" group and 80% of disabled people, but was more successful for young people.
The trial report says the fingerprint scanner was sometimes "too small to scan a sufficient area of fingerprint from participants with large fingers".
It also says the system must be capable of scanning people with fingers which will not provide proper prints, perhaps because of scars.
Iris scans worked for 96% of "quota" volunteers and 91% of the disabled group. Some glasses wearers failed the checks unless they took their glasses off.
The trials report says further trials were needed on some groups who experienced problems.
"For example, black participants and participants aged over 59 had lower iris enrolment success rates," it says.
The report also says most of the volunteers found the biometric scans and checks either the same or better than they expected.
The only concern was on positioning for iris scans, which 31% of disabled volunteers found "very" or "fairly" difficult.
The majority of volunteers also said they believed biometrics would help with passport security and preventing fraud and illegal immigration while not infringing their civil liberties.
Minister Tony McNulty denied the tests showed the technology discriminated against certain groups.
He stressed the trials were designed to discover how people found the scanning process, not test the technology.
"The database and the registration are central to this whole thing," he said.
"We get lost in this debate about the card itself. The interplay between the two is the key.
"These Orwellian pictures that are drawn up by some people miss the point entirely.
"The technology is moving in the right direction."