LONDON (Reuters) - Revealing the results of confidential government studies into the financial health of major British banks could cause uncertainty in financial markets, a finance ministry spokesman said.

Britain's Treasury said on Friday that it had rejected a request made under freedom of informaton legislation by news agency Bloomberg for publication of stress tests conducted by the Financial Services Authority earlier in the year.

"The information was withheld on the grounds of a number of exemptions, including that disclosure of such information may lead to uncertainty in the financial markets, either in relation to specific institutions or more generally," the spokesman said.

So far Barclays is the only major bank to have said that it passed the FSA's stress-testing process, despite others such as Royal Bank of Scotland and Lloyds Banking Group being tested around the same time.

The Financial Times said the stress-testing included looking at whether banks would have enough capital to survive a 50 percent crash in house prices and a two-year recession.

An FSA spokesman said it had also turned down a freedom of information request from Bloomberg. "If we did release any specific information on stress testing it would be as an announcement to the market via (press release news wire) RNS, so it's not something I can comment on at this stage," said Joseph Eyre, prhess officer at the Financial Services Authority.

The United States has already published the results of its stress tests, saying it would boost financial market confidence — a position supported on Friday by the Dutch financial market regulator AFM.

"Everybody is talking about a level playing field. There is an increasingly unlevel playing field between investors in American financial stocks and in European financial stocks," said AFM chairman Hans Hoogervorst.

"Investors in European financial stocks remain much more in the dark and there has not been — and I don't think it's going to be very likely — transparency in stress tests in the banking sector in Europe," Hoogervorst told a meeting of the Financial Crisis Advisory Group, which he co-chairs.

"This pressure is mainly exerted by bankers and ministers of finance, who are all bankers now, and obviously they have no natural interest in transparency," he said.