A war of words has broken out between two companies that want to build solar thermal power stations in South Australia.

Australian company Solastor has put up proposals to build a 170-megawatt graphite solar thermal plant in Port Augusta.

US company SolarReserve last year announced similar plans, but proposed a plant using molten salt instead of graphite.

Solastor's chairman, former Liberal leader John Hewson, says his competitor’s technology is outdated.

But the American firm says Solastor is spreading misrepresentations.

Solastor has released a frequently asked questions document to cast more doubt on the rival technology, which claims that molten salt plants create a “deadly zone” for birds, and require gas as a back-up energy source.

SolarReserve hit back this week.

“SolarReserve's technology has been proven to be safe for birds, with a full 12 months of data,” the company said in a statement.

“Solar thermal technology with molten salt energy storage does not require any gas back-up to maintain operating temperatures.”

Renewable energy media outlet RenewEconomy has slammed Mr Hewson’s “unexplained attack” on molten salt storage.