Passengers face massive delays at Gatwick Airport because of problems with new iris-recognition equipment, a Tory MP has claimed.

Ben Wallace said an official report on trials of the technology showed it had failed half of its assessments.

And he said it was further proof that Government plans to introduce ID cards were "running off the tracks" and could prove unworkable.

But the Home Office said the initial problems had been dealt with and the system - now in operation at several major airports - was a success.

Thousands more members of the public had signed up than expected, a spokeswoman said, and iris recognition remained "an option" for ID cards.

Mr Wallace told BBC Radio 4's Today programme: "The pilot failed half its assessments: it wasn't available when it was needed at the right level; when the system crashed, it took over eight hours to fix.

"Iris recognition is one of the main planks of the biometrics the Government said made their ID scheme foolproof.

"In an answer to me, the minister said that iris recognition had been chosen as a biometric because it outperformed all others.

"In this case, it doesn't."

Home Secretary John Reid last month dropped plans for a massive single database to hold records for the national identity card scheme. Three existing systems will be used instead to keep costs down.