Preliminary statistics released on Wednesday showed that 2009 would be a record year for the number of clean-tech venture capital deals worldwide.

There were at least 557 such deals in North America, Europe, China and India in the past year, market research company Cleantech Group and auditing firm Deloitte said.

The tally is preliminary, they noted, and is expected to increase by 5 to 10 percent once investors fully announce their activity in the whole year.

According to their preliminary report, clean-tech venture capital investments totaled at least 5.6 billion U.S. dollars last year, down 33 percent from 2008 and approximately equal with 2007.

But the two companies pointed out that compared with other sectors, investments in clean-tech declined less in 2009.

"Record levels of activity from investors, governments and corporations in 2009 demonstrated that the market for clean technologies continues to strengthen regardless of any non-binding global climate change agreement," Nicholas Parker, executive chairman of Cleantech Group, said in a statement.

In the private sector, about a quarter of all global venture investment capital was invested in clean-tech in 2009, "more than software, biotech or any other category," he said.