MADRID—Insurers that hoped the fifth quantitative impact study would be the final one before implementation of Solvency II may be disappointed by a European Commission official saying a sixth study can't be ruled out.

The QIS 5 survey of insurers by the Committee of European Insurance and Occupational Pension Supervisors is to begin late this summer. The series of studies is designed to shape the structure of Solvency II, the risk-based capital framework for insurers scheduled for implementation in late 2012.

Insurers and others have expressed concern that information in the fifth survey could lead to significantly higher capital requirements under Solvency II.

While that would be unexpected for the market as a whole, some individual insurers could see capital requirements rise, said Karel van Hulle, head of the commission's internal market and services unit.

During a panel discussion at the International Insurance Society's 46th Annual Seminar in Madrid, Mr. van Hulle also said QIS 5 will not necessarily be the final survey.

“If QIS 5 were to lead to the conclusion that what we have proposed…is not satisfactory, we may well want to do a further test, which we will call QIS 6, where we will test some targeted issues,” Mr. van Hulle said.

A sixth survey would not be as broad as QIS 5, he said, but, if needed, it would be carried out “so that we can take a final decision on the basis of facts, not on dreams or theories.”

Greg Carter, managing director at Fitch Ratings in London, said during the panel discussion that insurers can expect higher capital requirements as a result of QIS 5.

“QIS 5 is going to raise the bar in terms of capital requirements,” Mr. Carter said. “For many of you in the room, you'll be relieved that it's not as high as it could have been, but certainly our view is that it's going to raise the bar.”

Mr. van Hulle said the commission “would be surprised if, for the industry as a whole, Solvency II will lead to higher capital requirements.”

Companies underwriting “risky business,” however, may have to increase capital “because we will go for a full risk-based regime,” Mr. van Hulle said.

While it is difficult to predict which or how many companies would be potentially short of capital under QIS 5, it is reasonable to expect that if the survey “raises the bar,” there will be more than the few found by QIS 4 to be in need of boosting capital under Solvency II, Mr. Carter said.

Companies that find themselves undercapitalized may find it difficult to raise additional funds, Mr. Carter said.

“I can think of one company in particular that looked to the equity markets to raise capital” to fund an acquisition and “got rebuffed,” said Mr. Carter, who did not elaborate. “The debt markets can be even more fickle. Over the last few years, it's been difficult for all but the strongest companies to tap those markets.”

Other capital-raising measures such as securitization “have been difficult in volatile markets and we have seen a number of capital-market transactions recently that have either been scaled back or abandoned,” Mr. Carter said.

He said the results of QIS 5 will help Fitch “focus on the capital landscape” in the rating agency's work to assess Solvency II's effect on insurers' financial strength.

“But we must not lose sight of the fact that capital is just one part of our analysis and there are many other things that go into the rating process,” he said. “What is clear is that there will be some companies that need to raise capital or reduce risks, and those companies that can't do that quickly or easily will face challenges.”

Also on the panel were Ricardo Lozano, director general of Spanish regulator Directorate General for Insurance & Pension Funds in Madrid; and Roger Sellek, managing director, global financial services at A.M. Best Co. Inc. in London. The discussion moderator was Therese M. Vaughan, CEO of the National Assn. of Insurance Commissioners in Washington.