EXPERTS last night played down fears of a terrorist threat to water supplies amid claims that a reservoir was to be fenced off to prevent an attack.

Reports yesterday said water bosses had been asked by Government officials to secure one of Scotland's largest reservoirs, Mugdock, near Glasgow, to prevent the possibility of water supplies to hundreds of thousands of people being poisoned.

Alistair Baker, of Northumbrian Water, which has 2.5m domestic water customers, said last night that he could not comment specifically on the reports.

"We have a rigorous testing regime and make constant checks on the quality of our water. Fencing off reservoirs would be impractical given their size," he said.

Kielder, in Northumberland, the water company's biggest reservoir has 27 miles of shoreline.

A university professor, who did not want to be named, said: "It would be far from easy to mass contaminate a water supply."

Any move to fence off reservoirs was described as "speculation" by the Home Office.