A fourth train service on the Warrnambool line on Sundays would help address overcrowding, according to Member for Wannon Dan Tehan.
"The timetabling seems to be completely out of whack with community demand for the service," Mr Tehan said.
"Especially on a Sunday when people are travelling to and from home after spending time away at the weekend."
His comments come after a number of people were forced to stand or sit on the floor on Sunday because there were three carriages on the train instead of five due to a maintenance issue.
Mr Tehan said it was extremely disappointing given the federal government's investment of $104 million to upgrade the Warrnambool to Melbourne line.
"The state government has failed to invest that money and to invest it properly," he said.
"It seems, if anything, the rolling stock seems to be going backwards."
Glenelg Shire mayor Anita Rank, who was on the overcrowded train service on Sunday, said country residents were being treated like second class citizens.
"Why do people who travel the furtherest actually get the worst trains from a comfort perspective?" she said.
"Metro trains are clean, neat and fast and you actually get internet connectivity on them."
Cr Rank said she also believed the lunchtime service on Sunday should have a connecting coach to Portland.
"I would always advocate for more services but an additional service will only work if there is a connecting bus (to Portland)."
She said Portland residents either had to choose to take the early morning service or the night service as the lunchtime service didn't have a connecting coach to the city.
"On a Sunday night getting into Portland at 12.50 or 1am doesn't cut it for people who have to work or go to school," Cr Rank said.
A Department of Transport spokesman said the state government would "continue to review and invest in the regional train network to deliver the best possible services for passengers and meet growing demand".
"We're currently upgrading the Warrnambool line to improve train frequency and reliability, while paving the way for modern VLocity trains to run on this line for the first time," the spokesman said.
Have you signed up to The Standard's daily newsletter and breaking news emails? You can register below and make sure you are up to date with everything that's happening in the south-west.