In a sign that US electricity companies are recognising that the Democratic-controlled Congress will seek to impose aggressive climate change initiatives, six companies, including Exelon, one of the largest utility companies, on Wednesday endorsed a bill that would reduce their projected emissions by 25 per cent below projected levels by 2020.

Dianne Feinstein, the Senate Democrat from California, and co-sponsor of the cap and trade bill with Tom Carper, a Democrat for Delaware, said the bill was the first time “major industry groups have endorsed a cap and trade bill which establishes emissions reductions as deep and aggressive as this bill”.