Incumbent MP Roma Britnell launched an "Our Roads Are Not OK" campaign on September 16, blaming the Andrews Government for the poor state of south-west roads.

Ms Gaston said while Ms Britnell had been vocal about Labor neglecting rural and regional roads, the historical record told a different story.

"Funding for roads in the south-west has doubled since the Liberal and National Coalition was last in power," Ms Gaston said.

"The Andrews Labor Government has made a $780 million investment in south-west roads, which will rebuild, repair and resurface more than 245 kilometres of roads across the region."

Ms Gaston said it was easy to make promises when your party wasn't in power. Ms Britnell has been in opposition since she entered parliament in 2015.

"Who do you trust more, a government that is making real investments in rehabilitation and maintenance of our roads right now, or the people who make promises and never deliver?" Ms Gaston said.

"I know we have to do work on this and the roads aren't great, but the investment we have made is enormous."

She said the crumbling road network had been an "overriding theme" of recent visits to Portland and Terang. "I understand and have heard people's frustrations."

September marks the start of the road maintenance season in the south-west and Ms Gaston said wet conditions had made road conditions particularly bad as crews started a maintenance "blitz".

She said workers would spend the next eight months delivering more than 165 individual projects across major arterials like the Princes Highway, Henty Highway and Glenelg Highway, as well as key routes like the Woolsthorpe-Heywood Road.

The state government manages arterial roads and highways across the state, while councils manage local roads.

Ms Gaston said it wouldn't be a quick fix, with ever-heavier vehicles pummelling aging infrastructure. "One of the biggest problems is we have trucks that are so heavy driving on roads from the 1950s," she said.

She said she didn't know when work would start on repairing the Princes Highway west of Warrnambool, which was originally scheduled to begin in 2020. Works on the highway to Warrnambool's east have run years overtime.