"I criticise the perception that the financial markets have of themselves," she told the Münchner Merkur newspaper in an interview to be published Monday.
"They have opposed for too long the introduction of rules with the backing of the British and American governments," she said. "On top of national rules, we need more international agreements to stem irresponsible financial speculation."
Merkel recalled that when Germany headed the G8 group of industrialized nations last year, it had advocated greater transparency in international financial transactions, especially in hedge funds.
But the United States and Britain "did not back this to the degree required."
Central banks worldwide have this week pumped hundreds of billions of dollars into money markets left severely unsettled by the collapse of US investment bank Lehman Brothers.
On Friday, the United States promised a bail-out package to take over bad debt costing hundreds of billions of dollars.
The German leader also slammed German public bank KfW, which transferred €300 million to Lehman Brothers on Monday, after it crashed.
"It's only normal that consequences will follow" for KfW officials, she said, adding that it was only to be expected that they "carry out their work responsibly."