The credibility of the European Union's flagship carbon trading scheme has been dealt a blow after carbon prices fell to six-month lows following the UN talks in Copenhagen. Traders and analysts say low prices could continue well into 2010, slowing investment in low-carbon technologies which have already been dented by tight financing due to a slow economy. "(The low price) reinforces the idea that relying solely on the EU ETS to drive investment is probably not the answer at the moment," said Andy Kelly, head of business development at Centrica. "This does give ammunition to the anti cap-and-trade brigade," an emissions trader said, referring to groups who say emissions trading does not work. The European Union's Emissions Trading Scheme (EU ETS) imposes a cap on carbon emissions from power plants and factories in the 27-nation bloc using a fixed quota of EU Allowances (EUAs). Prices can directly influence the daily operation of power generators, encouraging them to switch to gas from heavy-carbon coal, or make investments in renewable sources of electricity. Low prices directly benefit fossil fuel energy production. The scheme is sometimes criticised for not spurring low-carbon investment fast enough. Utilities say they need certainty from a prolonged and sustained rise in carbon prices to invest in new nuclear plants and carbon capture and storage. Many analysts say EUAs need to rise to 25-30 Euros or even higher to spur such investments but prices are not forecast to reach that level until 2012 or beyond.