Ministers refuse to say what the threat means for Britain

Ministers were urged last night to make public the exact scale of the terrorist threat to Britain in the wake of the heightened security alert in the United States.

Ministers were urged last night to make public the exact scale of the terrorist threat to Britain in the wake of the heightened security alert in the United States.

While armed officers sealed off New York streets and stepped up the protection of financial institutions in Washington and Newark, no extra police officers were deployed in this country.

A series of newspaper reports yesterday morning suggested that American banks in the City and Canary Wharf could be in the bombers' sights.

But both the Government and counter-terrorist sources said nothing had been changed by the revelation that computer files from captured al-Qa'ida suspects had named potential targets for attack in Britain.

Scotland Yard received calls from London-based bankers and city chiefs alarmed at events in the US but its advice was not to panic. City institutions were just told to make sure that their existing checks and security procedures were working.

The Metropolitan Police anti-terrorist branch has been working with financial institutions to ensure they have drawn up emergency plans to deal with a terrorist attack. Those include the evacuation of staff and the setting up of secret satellite offices that can be run by a skeleton staff.

Anti-terrorist sources said there was no specific information about targets in Britain contained in the material from Pakistan or any intelligence that needed to be acted upon immediately. Sources also said that any suggestions that the computer data had placed Britain under an imminent threat was alarmist.

One city insider accused sections of the media of "irresponsible sensationalism", adding: "The feeling from the Home Office, Metropolitan Police and other London banks is that the story has been blown out of proportion. Security has been high since 2001 and investment banks remain vigilant."

At the London Stock Exchange, whose previous building was hit by an IRA bomb in 1990, a spokeswoman added: "We have quite detailed plans for a wide range of potential contingencies which are tested regularly. It is business as usual. Obviously people are aware. This is a high profile building and we are in high profile area. It is second nature for people to be alert to that kind of thing."

Hilary Cook, of Barclays Stockbrokers, said it was indicative of the mood over the last few years that the market had not suffered. "It did not react more negatively yesterday because people have believed for some time this war on terror clearly has not been won and it will cost a lot of time and money to win it," she explained.

Professor Chris Brady, a security analyst and lecturer on business intelligence at the Cass Business School at the City University in London, said: "Since 2001, it has become totally unacceptable to withhold security information. This means that almost every day in the United States there is a public announcement about security issues. It is the kind of information that five years ago would not have reached the press.

"That allows the media to pick a sexy line from a large amount of material, however vague. If it is a quiet news day it is terribly easy for the press and broadcasters to blow something up very quickly."

The Conservatives called for the Government to give more information to the public after it confirmed this country's level of security alert would not be affected.

They demanded the appointment of a minister to co-ordinate domestic security and suggested Britain could examine whether to establish a US-style colour coding system to indicate the level of alert.

David Davis, the shadow Home Secretary, said: "We are much more secretive than the Americans - I think we have to have a much better balance." He also claimed the US was at a "much more advanced stage" in planning for a disaster, such as a terrorist strike.

But the Home Office was resisting pressure to give a "running commentary" about security activity. A spokeswoman said: "The continuing level of threat has remained high for some time. We have said we won't hesitate to warn the public if there is a specific threat."