Thirty-six kilometres of new lanes to combat congestion on Monash and Princes freeways

The federal and state governments have pledged an extra $367.5 million to combat rising congestion on Melbourne's increasingly cramped arterials.

Prime Minister Scott Morrison and Premier Daniel Andrews came together to announced an extra 36 kilometres of new lanes in the second stage of the project to expand the city's Monash Freeway.

The new injection brings the overall cost to about $1.1 billion, with the governments attributing the ballooning price tag to rising labour force costs and more expensive raw materials.

The regularly-congested freeway will go from having eight lanes to 10 between Springvale Road while further along the south-east corridor, the Princes Freeway will increase from four to six lanes between Clyde and Cardinia roads.

Construction will start in late 2020, and is expected to be completed in late 2022.