The Observer has established that under new plans to combat terrorism, the US government will demand that visitors have all 10 fingers scanned when they enter the country. The information will be shared with intelligence agencies, including the FBI, with no restrictions on their international use.

US airport scanners now take only two fingerprints from travellers. The move to 10 allows the information to be compatible with the FBI database.

'We are going to start testing at several airports,' a Department of Homeland Security spokeswoman confirmed. 'It will begin some time this summer.'

Sources said 10 airports would initially be involved. The scheme will cover most of the major airports frequently used by British travellers, including New York, Washington and Miami. Countries subject to the new scheme include Britain, other European Union nations, Japan, Australia and New Zealand.

Last night the British civil rights group Liberty expressed astonishment at the plan, which will affect four million British travellers to the US. 'This must be the Keystone Cops school of border control,' said Shami Chakrabarti, director of Liberty. 'Accumulating the fingerprints of millions of innocent passengers will not deter would-be suicide bombers.'

Security experts warned the scale of the scheme might jeopardise its success. 'This maniacal proposal will turn thousands of law-abiding British travellers into terrorist suspects,' said Simon Davies, head of Privacy International, a campaign against intrusive surveillance.

'The technology at US airports will be far less reliable. That means anyone could be the victim of a false match, Davies said. 'Be warned. A San Francisco Bay family holiday may easily become a nightmare.'

He predicted that airport queues would treble as a result of the scheme. 'Taking fingerprints is a delicate and complex undertaking that can't be rushed to keep queues short,' he said.

A recent report by the civil liberties group Statewatch highlighted a Japanese study that tested 15 biometric systems and found 11 of them failed to detect 'false' fingerprints were being used in the form of a latex strip covering a person's fingers.

Britons already have their credit card details and email accounts inspected by the American authorities following a deal between the EU and the Department of Homeland Security. Now passengers face having all their credit card transactions traced when using one to book a flight. And travellers giving an email address to an airline will be open to having all messages they send and receive from that address scrutinised.

The demands were disclosed in 'undertakings' given by the Department of Homeland Security to the EU and published by the Department for Transport after a request under the freedom of information legislation.

In America, the 10-digit fingerprint plan has sparked concern among civil rights groups, which accuse the government of using the excuse of terrorism to expand its ability to monitor individuals. The scheme uses an electronic scanner. Fingerprint information is then fed into a Department of Homeland Security database that stores material from domestic security organisations such as the FBI, as well as international bodies like Interpol. It already holds 71 million fingerprints and is growing.

'This is about stopping crime and about national security after 9/11,' the Homeland Security spokeswoman said. 'The reason for 10-digit fingerprints is that it is more secure than the two-digit system, and the 10-digit system is becoming the international standard.'

The spokeswoman said she was confident the new procedure would not deter people from visiting the US. 'That is what people said when we introduced the two-digit system,' she said. 'But that is not what happened.'

She added the reason the scheme was to run in just 10 airports initially was to ensure its smooth operation before it became standard at all US airports, major ports of entry and consulates abroad. The Department of Homeland Security aims to have the new system in place across the US by the end of 2008.

In a speech at a technology conference Michael Chertoff, the Secretary of Homeland Security, said the main aim was to deter 'the unknown terrorist'.

It could pick up on fingerprints left at terrorist sites around the world. 'A fingerprint that is left... in the training camp or in the safe house is, in fact, a powerful tool.' He added that he hoped the system would deter any terrorists from ever trying to enter the US. 'We will have a world in which any terrorist who has ever been in a safe house or has ever been in a training camp is going to ask himself or herself this question: have I ever left a fingerprint anywhere?' Chertoff said.