Carriers including Allianz SE, Europe's biggest, argue the rules will deprive them of a new area of investment that could help offset low returns on fixed income, where they traditionally had put most of their customers' money. The proposed level of capital requirements would put infrastructure and renewable energy investments in the same risk category as private-equity and hedge-fund commitments, which would be too high, they have said.

Discouraging insurers from making such investments "would have a significantly negative effect on the European economy at a time when boosting growth is an overall policy objective," Koller said.

Europe leads

Last year, Europe maintained its ranking as the world's biggest insurance market with 1.1 trillion euros in premiums, or 35 percent of the global market, compared with a 30 percent share for the U.S. and 28 percent for Asia, according to Insurance Europe.

Investments by European insurers increased 3.2 percent at constant exchange rates last year, led by life insurance, which accounted for more than 80 percent of total, the lobby group said.

Starting in 2016, the European Union plans to introduce Solvency II. The rules specify how much capital firms must hold to meet future obligations and to safeguard customers' money. The EU reached an agreement in principle on Solvency II last year after 13 years of wrangling with the industry, politicians and national regulators. Details including precise capital charges are still being negotiated.