Alinta Energy has given up the fight to keep its two ageing coal-fired power stations in Port Augusta in South Australia in operation, as a glut in power supply, made worse by the growth in renewable energy, foiled a $300 million effort to return them to profit.

Up to 478 job losses are expected from the shutdown of the Northern and Playford B power plants, as well as the Leigh Creek coal mine that supplies them, which will close by March 2018 and possibly earlier.

The power plants were widely seen by analysts as potentially vulnerable to closure in a market plagued by oversupply and weak wholesale power prices. Credit:Bloomberg

The job cuts will more than halve TPG Capital-owned Alinta's total workforce and prompted South Australia Liberal Opposition leader Steven Marshall to point to a "jobs crisis" in the state, which already faces the closure of the automotive industry in 2017 at the latest, when Holden is scheduled to stop vehicle manufacturing.

The South Australian government has promised support packages of at least $1 million for the affected communities at Leigh Creek and Port Augusta, and intends asking the federal government for extra help.