Millions of homeowners will be left without insurance against chemical, biological and nuclear attacks because Britain's leading insurance companies have changed their policies to exclude terrorism cover, The Times has reported.

The daily newspaper said several insurers, including R&SA and AXA, were following Norwich Union in amending their home and contents policies to exclude damage caused by a "dirty" terrorist attack.

Customers are notified of the changes when their policies come up for renewal.

Insurers say the change is a result of reinsurance companies refusing to provide terrorism cover after the September 11 attacks in the US, the paper reported.

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