PLANS to buy 52 trains and 50 trams for Melbourne, as well as 20 trains for regional Victoria, will be unveiled today as John Brumby seeks to lay claim to the title of "the public transport Premier".

The $4.2 billion buy-up of rolling stock will be accompanied by a promise to build Melbourne's first metro-style underground suburban rail line — a 17 kilometre cross-city tunnel from Caulfield to Footscray via St Kilda Road and inner Melbourne — as well as a new surface rail line through the rapidly growing western suburbs and a long-awaited extension of the Epping line in the north.

Premier John Brumby will today outline plans for more than 70 new trains and 50 trams. Credit:Penny Stephens.

The Age believes the Government's transport blueprint, to be revealed today, will involve nearly $40 billion of purchases and projects.

Mr Brumby will claim the plan will create tens of thousands of jobs and transform Victoria's road network and public transport system into Australia's best.