Biometric iris scans may be ineffective for up to one million people in the United Kingdom who are blind or have visual impairments such as cataracts, according to a report from the London School of Economics & Political Science.

If the U.K. parliament requires iris recognition technology for a biometric identity card for citizens, it would discriminate against people with deteriorating eyesight, said the report, titled “The Identity Project: An Assessment of the UK Identity Cards Bill and its Implications.”

The U.K. legislature currently is considering the Identity Cards Bill to create a national ID card with a computer chip containing iris and fingerprint biometrics.

The report identified shortcomings to the iris scan, among other problems. “There exists a threat that this technique may inherently discriminate against people with visual impairment,” the report stated. “The available literature indicates that blind and partially sighted people may be unable to use such systems, may generate unstable or unusable biometric data, or may suffer disproportionate disadvantage in using such systems.”

Visually-impaired people typically are excluded from iris scan research trials. “It appears no trials have been undertaken with specific reference to blind or visually impaired users,” the report said.

Yet iris-based systems may be problematic for large numbers of people, including those who have experienced eye injuries or surgeries, the report said. The 250,000 people a year who receive cataract surgery in the U.K. may experience rejection from an iris scan system after the surgery, and may need to re-enroll their irises in the system, the report said. People who suffer from eye tremors also may have difficulty presenting stable images of their irises to participate in the scanning systems. “Whether the estimated 60,000 or so people with Nystagmus in the U.K. will be able to use iris biometric systems will depend entirely on whether the government is prepared to ensure that appropriate iris camera equipment is made generally available,” the report said.

Furthermore, the report said some tests have found that up to 7 percent of iris scans fail due to watery eyes, long eyelashes and hard contact lenses.

Finally, iris scans, as well as fingerprint scans and other biometrics, can be “spoofed” with forgeries and counterfeit information, the report said.

Based on this and many other criticisms, the report does not recommend the National Identity Card proposal. “This report concludes that the proposals currently being considered by Parliament do not represent the most appropriate, secure, cost effective or practical identity system for the United Kingdom,” it said.

It advises alternative identity technologies in more limited forms, such as allowing consumers to access government services through the Internet.