The banks lent $5.4 billion for wind projects last year, a fall of 36% on 2011, and counter to the steady increase in investment in the sector since 2007.
This fall came in spite of a 19% increase in overall renewables investment to $108.9 billion. Wind generation was overtaken by hydroelectric power as the form of renewables to receive the most investment.
BNEF analyst Abraham Louw said: "The fall is releated to policy changes which are particularly acute in the US with the imminent end of the production tax credit. This has had a serous effect on development banks' willingness to invest in wind.
"We do not expect to see any further blips, and investment should start rising again this year. It should also be remembered that this money is still buying more in terms of megawatts due to the drop in the cost of wind."
Since large development banks like the European Investment Bank have ruled out investing in fossil fuels and an increased interest in renewables from banks in developing countries, the report predicts that there will be an overall increase in investment in renewable energy of between 15 and 30% in 2013.
Germany's KFW Bank tops the list of investors in clean energy with $34.4 billion injected in 2012, with China Development Bank coming in second with $26 billion invested.
Investment flows between developing countries reached an all-time high of $7.5 billion in 2012, not far behind lending from developed countries to developing countries.