Britain faces a severe risk of another terrorist attack, the government said Tuesday as it launched the country's first public terror alert system.

The threat rating — based on a U.S. Department of Homeland Security model — was reported on the Web sites of the Home Office and the domestic spy agency MI5.

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The system ranks threats as low, moderate, substantial, severe or critical and was introduced after criticism of the public's access to accurate information ahead of last year's deadly attacks on the London transit system.

British Home Secretary John Reid ordered the changes to simplify the previous seven-tier system, which was deemed too complicated and was not available to the public.

Britain had been at "severe general" level, equivalent to "severe" under the new system, since the Sept. 11, 2001, attacks on the United States, the Cabinet Office reported.

The Home Office said that under the new system, a critical rating would indicate there was strong intelligence of an expected imminent attack. A severe rating indicates that intelligence suggests an attack is highly likely, it said.