Mirant Corporation, the Atlanta-based electricity producer, on Tuesday night made an $8bn unsolicited approach to take over rival NRG Energy in a deal that would create the largest non-utility power company in the US, dominating the nation’s most populated regions.

The cash-and-stock bid from Mirant, which is supported by an $11.5bn financing commitment from JPMorgan Chase, was made public after NRG earlier this month rejected the offer.