Now the company is suddenly claiming that the 2002 agreement is invalid because of the 2006 legislation, and that only the federal government has regulatory power over nuclear issues.

PG&E had previously signed a power purchase agreement with BrightSource in April 2008 for 500 megawatts with an option to buy another 400 megawatts.

Mr Kennedy, the most prominent sceptic about the power-sharing agreement, was said to have informally discussed his worries with opposition whips.