The main opposition Democratic Alliance (DA) said on Friday it would seek an urgent update from State-owned freight and rail company Transnet on a protracted "go-slow" strike at its Ngqura port.

Workers have staged the protest action at the Ngqura container terminal for 13 days in a show of dissatisfaction about promotions.

This has forced truck drivers to wait up to 18 hours before they can drop off or collect goods, leaving products from the automotive, citrus, meat, textiles and electronic sectors stuck in transit.

On Thursday Transnet said it had suspended a number of its employees at the terminal in Port Elizabeth for engaging in illegal industrial action which had had hit citrus and automotive customers the hardest.

DA spokesperson on public enterprises Natasha Mazzone said strong and decisive leadership was needed at Transnet to avert what could potentially result in a loss of jobs and revenue.

"While we recognize the democratic right of workers to embark on a legal strike action, we are deeply concerned that 13 days have passed without a solution. Volkswagen, an employer of 6 000 workers, has been the hardest hit by this strike action, and it has reportedly lost 400 of its 680 production units per day," she said in a statement.

"A protracted go-slow of this level will have devastating effects, not only on the 6 000 currently employed by Volkswagen, but also on the other major industries which depend on the port. Should this go-slow continue, we risk companies taking their business to more stable and reliable shores."

Operations at the Durban container terminal have also been affected by equipment failure and high-level absenteeism and Transnet said it had also noted a decline in performance levels in Cape Town.

The State entity said it was continuously engaging customers to communicate business continuity plans including prioritising some of the urgent cargo.

Discussions were were also ongoing with labour unions to normalise port operations, Transnet said, adding that the impact of the protest on the economy had not yet been quantified.