AUSTRALIAN Labor party opposition to the expansion of Melbourne's port container facilities have won a concession from the Liberal government in the State of Victoria, which will now insist bidders submit a plan to avoid traffic jams.

The state-owned Port of Melbourne Corporation's CEO, Stephen Bradford, said more than 40 per cent of international container movements through the port were handled by trucks between 6pm and 6am on weekdays.

"That percentage is growing and we expect it to grow more," he told reporters.

But Mr Bradford recently added the condition that bidders to operate the new terminal would have to explain how they would have more off-peak truck movements, reported the Australian Associated Press.

The opposition has warned the new on-off ramps linking the M1 freeway to the Port of Melbourne under a A$1.20 billion (US$1.21 billion) redevelopment plan are a "recipe for traffic chaos". The redevelopment will include the construction of a new container terminal at Webb Dock and upgrades to the Swanston Dock to boost capacity.

The Port of Melbourne will borrow A$500 million to finance the project, while the remaining A$700 million will be provided by private stevedoring companies.

Ports Minister Denis Napthine said the new Webb Dock container facility will initially move at least one million TEU. "We will reaffirm Melbourne as the number one container port in Australia," he said.

Dr Napthine also said traffic management systems would be in place to ensure trucks from Webb Dock would use the M1 during the 20 hours of off-peak time. New on-off ramps will be built linking the port to the M1, the major freeway running through Melbourne to Geelong.