The European Union's insurance watchdog has launched a study of proposed capital and risk management rules, which insurers fear will make some of their staple products unviable.
The European Insurance and Occupational Pensions Authority (EIOPA) set a nine-week deadline for insurance companies to test what impact changes to the so-called Solvency II rules would have on their operations.
Insurers expect the study to show that a major rewriting of rules applying to life insurance will be needed, adding to repeated delays in the introduction of the new regime.
EIOPA expects Solvency II will come into force no earlier than January 1, 2016, but Germany's insurance watchdog has already said that a 2017 start may be more realistic.
"If these seemingly technical details of the new regime are not correct, the impact on the European insurance industry, its clients and the economy would be severe," said Olav Jones, deputy director general of Insurance Europe.
Some life insurance companies have said that Solvency II would make their products unworkable because they would be forced to hold so much more capital in exchange for selling products guaranteeing returns to customers.
With traditional guaranteed life insurance products, the insurance company bears the risk of covering the future guarantee, as opposed to index-linked life insurance, where the consumer bears all the investment risk.
The former type of products are particularly popular in Germany, France and Spain.
"Solvency II must not create unnecessary barriers to insurers providing guarantees for customers and investing long term, not least because the insurance industry is by far the largest institutional investor in Europe, with more than €7.7trn in assets," Mr Jones added.
European life insurance premiums totalled €633bn in 2011, according to industry trade body Insurance Europe.
Auditing firm KPMG said the long-term guarantee test and the analysis of its results meant a key European Parliament vote would probably take place after the parliament's summer recess, months later than expected.
"The time required for EIOPA to produce its report, expected in the second half of June, could itself result in further delays to the Solvency II timeline," KPMG said in a statement.
EIOPA said it hopes to bring forward parts of the rules where there is widespread agreement.