Laid-off Australian car workers would be ready to start work "at a moment's notice" if the former Holden factory in Adelaide is retooled to build electric vehicles, the manufacturing union says.

The South Australian government has revealed that British billionaire Sanjeev Gupta's GFG Alliance, which last year saved the troubled Arrium steelworks from closure, now has its sights on buying assets from Holden's defunct Elizabeth plant to "develop the site as a manufacturing base for an electric vehicle".

Holden closed its Elizabeth production plant on October 20, 2017 Thomas Wielecki

"We are incredibly excited and supportive of the GFG Alliance’s bid and subsequent plans to ensure the continuation of our very proud history of automotive excellence and innovation in South Australia,” SA Treasurer Tom Koutsantonis wrote in a letter to GM Holden.

The Australian Manufacturing Workers Union, the largest union that represented the plant's former workers, has called on the Turnbull government to back Mr Gupta's bid.

"I can't think of a better use for the iconic Holden site - and better future employment for our Holden workers - than a future-driven electric car plant," union state secretary John Camillo said.

"Any investment in manufacturing is welcome, and electric cars are the future."

Mr Camillo said the AMWU had worked with Mr Gupta when he purchased the Arrium steel and mining group, based in the South Australian town of Whyalla, and would be "keen to work with him again".

"We have highly skilled former Holden workers who would be ready to start at a moment's notice," he said.

Head of GFG Sanjeev Gupta visits the Arrium Steel plant in Whyalla, South Australia. AAP

General Motors Holden was the final car maker to shut down its Australian manufacturing operations in October last year, following the closure of Toyota's plant and Ford factories in Geelong and Melbourne.

Holden is in the process of decommissioning its 120-hectare Elizabeth production plant, which could take another 18 months.

A spokeswoman for GFG Alliance said the company could not yet comment on the proposal. GM Holden also declined to comment.

South Australian Premier Jay Weatherill said the electric vehicles represented an exciting new possibility for the state, "and we're prepared to get in behind it".

"We've got billionaires like Sanjeev Gupta and Elon Musk investing in South Australia ... wanting to be here to create the jobs of the future," he said.

"This is a very exciting advanced manufacturing future for our state."