Underwriters said they would not be withdrawing cover for clinical trials following the drug trial for TGN 1412, which left six men seriusly ill.

The Medicines and Health-care products Regulatory Agency (MHRA) is now conducting an investigation after the drug, designed to tackle auto-immune diseases, super-activated the immune system, causing severe inflammatory swelling of the subjects.

Chris Tait, Chubb's European life science undewriter said: "We're committed to providing cover- insurance is compulory as a result of the EU Clinical Trials Directive."

While most trials are without serious incident, Tait added: "No trial can be said to be totally safe. We can never be complacent."

Markel (UK) recently entered the sector, with a new policy, Specialty Liability, for the medical, surgical, pharmaceutical, cosmetic and scientific equipment industries.

Managing director Steve Carroll said: "We're aiming at start ups and incubators with turnovers of less than £20m and a maximum sum insured of £5m."