Workers at Fremantle’s inner harbour will stage a 24-hour strike on Friday that is set to disrupt shipping at the busiest container port on Australia's west coast.

The strike, which has been called by the Maritime Union of Australia (MUA), will begin at 10am local time (0200 GMT).

The industrial action is spilling over from a dispute at Fremantle Port’s Kwinana Bulk Terminal that has been ongoing since 15 May.

A strike by inner harbour workers will prevent vessels from being tied up or let go at any berths in Fremantle's port including the container terminals.

A shipping list posted on the Fremantle Ports' website indicates that movements involving at least nine vessels including containerships, bulkers and tankers could be impacted.

Fremantle Ports told TradeWinds that it was working with customers “to ensure tomorrow’s 24-hour industrial action in the Inner Harbour will have limited impact on operations”.

The MUA called the strike in response to what it claimed was Fremantle Ports’ decision to stand down all workers at the Kiwana Bulk Terminal any time a workgroup undertakes industrial action, a move it claims shuts down the terminal for five hours per day and threatens to cause significant port delays.

Jeff Cassar, assistant branch secretary at the MUA of Western Australia, said: “Workers were simply exercising their legal rights as part of negotiations for a new enterprise agreement that reflects industry standards, yet Fremantle Ports' response has been aggressive, heavy-handed."

Fremantle Ports said it had been in discussions and "good faith negotiations" with the MUA over the enterprise agreements for operational and stevedoring employees for 18 months.

The industrial action at the terminal takes place between 4.30am and 7am each morning and again between 4.30pm and 7pm each evening.

“The outcome of these stoppages is there is no useful or meaningful work for employees across a five-hour period each day,” Fremantle Ports said. "During this time, the port is unable to safely load and unload vessels."

Cassar said Friday’s strike is aimed to bring the dispute to a head, rather than allow the stand-downs to continue to cause financial hardship for workers and customers of Fremantle Ports.