The £2.5m robbery prompted national security fears last week.

Eric Skinner, chief executive of Entrust told PrintWeek that banks could be duped by the false documents if they hadn't purchased passport readers authenticate the items.

However, he said that the stolen passports would be unusable at border control because of the security technology embedded in the built-in chips.

"Biometric technology adds a real deterrent," he said. "Even if a criminal could put a photo in the passport itself, there is now also a record of the photo imbedded in the chip, which would require getting past some of the most sophisticated encryption technology in the world.

"When a citizen goes through passport control their photograph would appear on a screen to be checked, along with other details including fingerprints."

Entrust said even if data is copied onto the chip embedded in the passport, the combination of high-entropy biometrics and digital signatures prevents an impostor from making use of a stolen e-passport.

Oldham-based printing company 3M Security Printing and Systems, which had produced the stolen passports, declined to comment.

A man, believed to be one of the deliverymen in the van, has been arrested on suspicion of conspiracy.