About 600 workers at General Motors Australian unit Holden's vehicle assembly plant in Adelaide have applied to take a voluntary redundancy package, according to a local report.

The company told the AAP news agency that staff from various divisions had applied for the package, in line with Holden's decision to axe that many jobs at the Elizabeth facility.

A Holden press release on 5 March said the automaker would reduce its South Australian operations by 600 positions "in coming months" due to increased plant efficiency following an $A532m investment in the Elizabeth plant and the phase-out of VZ Commodore models in 2007 as the new VE Commodore comes on-stream.

Holden said the VE was easier to manufacture than previous Commodore models.

"Maximising plant efficiency is a critical factor in Holden's future business strategy to secure a long term future in Australia and maintain competitiveness as a global automotive manufacturer," the company said, adding that daily production would be gradually revised from its current level of 620 cars to approximately 520 cars in March, and then back to maximum capacity of 620 cars per day by October 2007.

National manager of media relations John Lindsay told AAP the company was sifting through the applications and some could be approved as early as Friday.

He reportedly said most of those to leave would do so in April but some people in skilled positions could be asked to stay on longer.

"We have managed to achieve the 600 positions through voluntary processes. We will be assessing all the applications and be starting to inform staff on Friday. In most cases staff will probably finish in April," he was quoted as saying.

The cuts will reduce Holden's South Australian workforce to about 3,450 AAP said, noting that no jobs would be lost at the company's Melbourne engine plant.