Banks expect to continue to tighten their credit rules on loans to firms in the third quarter, the European Central Bank said on Wednesday.

In its latest quarterly Bank Lending Survey, the ECB said the sovereign debt crisis made it more difficult to get funds in the markets.

"In the second quarter of 2010, negative spillover effects from the sovereign debt crisis appear to have worsened banks' ability to obtain funding," the survey said.

"Hence, banks reported that access to wholesale funding became more difficult compared with the first quarter."

Over the next three months, banks expect that the difficulties in wholesale funding will remain, but to lesser degree than in April-June, it added.