The West Gate and Bolte bridges will need to be strengthened and the western end of the scrapped East West Link needs to be built to cope with a fivefold increase in container traffic at the privatised port of Melbourne, its new operators say.

The port's new owner, the Lonsdale Consortium, says the port could grow to handle between 12 and 15 million containers a year, up from 2.5 million now, ensuring that Melbourne remains Australia's busiest container port for the next 50 years.

Webb Dock when under redevelopment in 2015. Credit:Joe Armao

After paying $9.7 billion last year for a 50-year lease, the consortium wants big changes to Melbourne's roads and rail lines to help deal with a huge jump in freight traffic.

The changes would help grow the port's capacity and maximise the consortium's return on its investment, but it wants the Andrews government to make a series of tough political calls to help it achieve this ambitious target.