The Lloyd's of London insurer later issued a statement, at the request of Britain's financial regulator, which included the extra details. It described the details as a "clarification," and said it did not believe they constituted inside information.

On Monday, Hiscox warned the combined ratio - a key measure of profitability - in its retail arm would deteriorate to 97-99% this year before improving to 90-95% over the "medium term".

A ratio below 100% indicates an insurer is receiving more in premiums than it pays out in claims. The ratio for the retail arm was 93.6% at the end of last year.

In subsequent meetings with analysts, the company said it expected the ratio to fall to 96%-98% in 2020 and 95%-97% in 2021, before reaching 90%-95% in 2022.

RBC, Jefferies and UBS, which had cut price targets on Hiscox shares on Tuesday immediately after the trading statement, lowered them again after the analyst meetings.

JP Morgan also cut its price target and downgraded the stock to "neutral" from "overweight."

"We were left with the distinct impression that Hiscox is preparing for a casualty catastrophe, the likes of which haven't been seen since the turn of the century," Jefferies said.

Hiscox said it gave the detailed information in response to questions from analysts about the meaning of medium term, and that it expected to exceed its "conservative" estimates.

"The Group did not believe that this constituted inside information, rather it was a clarification of the meaning of 'medium term'," it said in its statement.

"The FCA (Financial Conduct Authority) asked us to make an announcement and we were happy to do so," a spokesman added.

Hiscox stock suffered its worst one-day fall in 17 years, ending 10% lower at the bottom of Britain's blue-chip share index.

(Reporting by Muvija M and Noor Zainab Hussain in Bengaluru; Editing by Mark Potter)