Australian ports will be crippled within days and state economies can expect further blows from the customs computer crisis, state authorities warned today.

The NSW government today said the problem-plagued computer roll-out, which has left the nation's ports clogged, was a case of gross mismanagement by customs and the federal government.

NSW Ports Minister Eric Roozendaal warned the backlog of shipping containers could lead to Sydney's Port Botany being filled to capacity by Wednesday, which would force ships to anchor off the coast waiting to unload.

"I am advised that the port (Port Botany) could experience major shipping delays on Wednesday, with ships queued off the coast waiting to unload," Mr. Roozendaal told reporters today.

"This is gross bureaucratic bungling by the customs service and the Howard government. This is damaging the NSW economy, ships are arriving for the Christmas peak - there couldn't be a worse time to introduce a new computer system.

The Port of Melbourne is also at breaking point and could be in the same situation by the end of the week, said Melbourne Corporation chief executive Stephen Bradford.

Problems with the Integrated Cargo System (ICS) computer system have caused major delays in clearing containers full of imported goods, leading to the backlog.

In Melbourne, there were 8600 import containers on the wharf, of which 3100 were cleared for collection. Bookings indicated 1600 could be moved today.

But Customs, Brokers and Forwarders Council of Australia executive director Stephen Morris said a complex series of hurdles between transport companies' travelling times and booking times to pick up the freight from the port would delay clearance of the backlog.

He said containers cleared today would most likely be moved on Wednesday.

"Customs have this thing in their mind that you can just haul a truck from somewhere, go down the road and pick up containers," Mr Morris said.

"That's not how it operates. You must get a slot time through the vehicle booking system that Patrick and P&O run to go in there."

The federal opposition said Customs Minister Senator Chris Ellison was fast becoming the Grinch who stole Christmas as stocks of popular toys might not reach shops.

Opposition Customs spokesman Senator Joe Ludwig said the botched implementation of the new computer system was to blame for the situation.

"The changeover to the Integrated Cargo System comes right in the middle of
the busy pre-Christmas importing period when popular goods and toys enter
the country," he said.