A terrorist threat to poison water supplies led to a big security alert at reservoirs and treatment works across Britain, it was claimed yesterday.

Water companies were allegedly ordered last summer to increase their security to prevent contamination of the supply. A publicity blackout was enforced to avoid causing panic.

Details emerged this week when Northumbrian Water executives gave evidence to an employment tribunal in Newcastle upon Tyne. They cited the emergency as a reason for dismissing an employee who had not responded adequately to an intruder alarm at works near Wooler in September. Michael Baker, the company’s network control leader, said: “What made this incident far more serious was the heightened security alert over an undisclosed and direct threat to contaminate water supplies.

“The Government warned all water authorities to be on high alert against possible terrorist threats.”

Richard Warmeford, production manager, said that the lapse had to be treated seriously. “Contamination did not occur in this case, but the need for security is extremely high.”

Security sources said that water companies received regular advice but there had not been any specific intelligence from last summer that terrorists were targeting the water supply.

The company’s former employee withdrew his unfair dismissal claim.

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