The off-again on-again $1.3billion project for 11.4kilometres of track will begin next year, he said.

It has been a year since the Glenfield-to-Leppington project, to service new housing estates, was deferred in the state mini-budget.

The project, expected to be completed by 2016, was announced in 2005 by former premier Bob Carr to be finished by 2012.

Mr Rees said this week the announcement was part of a ``fresh approach''.

``This Government will be judged on action, and when I said I would start delivering, I meant it,'' he said.

``You will see more of my own agenda and major changes because that is what the people of NSW have demanded of me.

``This is a fresh approach.''

He attributed his change of stance to the lobbying of MPs Geoff Corrigan, Graham West and Andrew McDonald.

Rail, Tram and Bus Union NSW president Alex Claassens said the union told the State Government that it could not ignore the public transport needs.

``Local governments, community groups and environmental groups have all joined in the campaign for more investment in rail infrastructure,'' he said.

``In the past week we have seen the State Government withdraw its controversial plan to rip up rail corridors and now it has brought back the South West Rail Link.''

Mr Claassens said the State Government needed to consult commuters and public transport workers, not just property developers and business lobbyists.

``Public transport workers know the system better than anyone, and they are passionate about their jobs,'' he said.

``They know the problems and solutions.''