A government intelligence agency has warned that current biometric technology may not be good enough for internal Whitehall use, according to a document leaked to Computing.

The findings do not cover citizen-based identification, but the concerns will raises questions about the viability of biometrics for the proposed national identity card scheme.

The 'Electronic Information Processing Security Notice S(E)N 03/04' was produced by the Communications Electronics and Security Group (CESG), the part of GCHQ that advises government on technology.

The Notice is an interim statement by CESG pending the release of Memo 28, a long-awaited guidance on security standards and policy for using biometrics in government.

'In some cases, Memo 28 will place stringent requirements on security that many currently available biometric products would find hard to meet,' it says.

The Notice also says the technology is 'inherently not secret.'

According to insiders, CESG is privately advising that biometrics is still an unreliable technology and it would be best to wait for three years for it to mature.

The government this week launched a six month trial of biometric systems. The UK Passport Service will test facial, iris and fingerprint recording and recognition. Some 10,000 volunteers will receive a personalised smart card carrying printed and electronic information.

The Home Office says work on a biometric for ID cards is still in an early stage.

'When we announced the biometric pilot for the Passport Service that specification was agreed by the International Civil Aviation Organisation and the Passport Service actively supported that development. At the moment nothing is up and running. We are going to be looking at the results from the biometric pilot studies that are being carried out,' said a spokeswoman.