"Locals are justifiably protective of their rail line," he said.

"This community still remembers having to fight to keep the line between Williamstown and Newport open back in the 1990s when Jeff Kennett was premier of Victoria. It took a Labor government to keep the Williamstown line operational."

Western Metropolitan Liberal MP Bernie Finn said disruption to the Williamstown line was typical of the Government's attitude towards the western suburbs.

His Greens counterpart in the upper house, Colleen Hartland, said she was involved in the original campaign to keep the line open. "Once they start to close it occasionally, they might try to close it completely."

She said Mr Finn was in no position to comment.

Metro communications manager Lanie Harris said buses replaced trains on sections of the Alamein and Williamstown lines on Monday last week because of train faults that developed due to the extreme temperatures.

"We would always prefer to run a full train service on every line at all times, but when we are faced with extreme conditions we have to make some tough decisions about efficient management of the fleet, and bus replacement is part of that plan."