"We need to emphasise continually that undue incentives to buy any asset class should not be part of a risk-based, prudent regime," Gabriel Bernardino, chairman of the European Insurance and Occupational Pensions Authority (EIOPA), told a financial conference on Wednesday.

European politicians want insurers to put more of their 8.5 trillion euros (7 trillion pounds) in assets under management into investments that will boost the bloc's struggling economy.

To revive growth, European Commission President Jean-Claude Juncker is also preparing a 300 billion euro investment plan aimed at luring private-sector financing.

Big insurers like Allianz (>> Allianz SE), Axa (>> AXA) and Generali (>> Assicurazioni Generali SpA) are looking to make long-term investments, such as in infrastructure or clean energy, that match their commitments to policyholders often decades in the future.

But they say European capital rules coming into force in 2016 make it too expensive for them to invest in these assets and are pushing for a better deal from regulators.

"We are all struggling to find good investments," Laurent Clamagirand, group Chief Investment Officer at Axa, told the conference. "The design of the Juncker plan is quite important."

Insurers see a stable economic environment and regulatory certainty as essential, Jaroslava Korpanec, Managing Director at Allianz Capital Partners in London said.

"It has to be a framework that protects investors against external risks, such as retroactive changes or expropriation."

Allianz is one of the partners in the Gassled natural gas pipeline suing Norway over its decision to cut gas transport tariffs, saying it could cost them billions of dollars.

SOLVENCY RULES

Insurers complain infrastructure investments in the so-called Solvency II rules could face capital buffer charges of up to 70 percent, while real estate investments are much lower, at around 25 percent. But they hold out little hope of getting the rules revised before 2018.

Bernardino said insurers must not focus on stand-alone risk charges in the rules.

"If we base our analysis on the marginal return on regulatory capital, investments in high quality securitisations, infrastructure debt and private equity are, at least on a relative basis, quite attractive," he said.

EIOPA said it would collect data on the riskiness and performance of infrastructure and other investments but for now it was standing firm.

"We will always base our opinions and advice on calibrations on evidence," Bernardino said.

Bernardino declined comment on the results of insurer stress tests due out later this month and said EIOPA was moving ahead with plans for stress testing the pensions sector next year.

(Editing by Thomas Atkins and Pravin Char)

By Jonathan Gould

Stocks treated in this article : AXA, Assicurazioni Generali SpA, Allianz SE