Premium rises of up to 600% on pharmaceutical risks are predicted after the recent onslaught of high-profile US legal cases.
Litigation is making drug companies virtually uninsurable.
Zurich London head of corporate underwriting Neil Lightbown said: "Rates are going up from between 50% and 500%. We are hearing of six-fold rises and huge increases in self-insured retention."
Unlike most lines of business, pharmaceutical risks have been unaffected by World Trade Centre losses. But premiums are now rocketing due to the size of claims, especially in the US.
GAB Robins national account director of North American business Paul Smith said there has been a growing number of court cases in the US, blaming certain products for adverse reactions and ailments such as skin cancer.
He said: "Underwriters, especially in the US, are turning away business because of the exposure. Exposures associated with pharmaceutical insurance in the London Market are growing each year. Underwriters are now having to cover potential costs for attorneys.
"Lloyd's will not write this type of casualty risk as it is huge."
Lightbown said insurers are afraid to underwrite pharmaceutical risks as all policies automatically include cover for legal expenses.
"Pharmaceuticals in the US will get sued at some time," he said.
Although there are many new products available on the market and the internet, Smith said underwriters were still hesitant to insure them. He said there were fears they had not been "particularly well monitored".
Smith added manufacturers often print waivers on product boxes saying they are not responsible for any adverse reaction. This leaves insurers liable for damages and payments if a claimant is successful in court.