A concept plan for Glenfield station's redevelopment and the 13-kilometre rail corridor has been approved and an environmental impact assessment is under way.

But Transport Minister David Campbell said the rail link's future is still uncertain, in spite of these developments as Treasury officials determine which capital works projects to potentially cull from the mini-budget.

Upper House Shooters Party MLC Roy Smith questioned the minister in a budget estimates committee hearing last week.

The Advertiser has learned that some found Mr Campbell's answer surprising in that he went into detail about how far the project had progressed.

This prompted comments that perhaps the rail link from Edmondson Park to Leppington would be saved in the mini-budget, even though Mr Campbell's said it was under review.

``The allocation of capital funds for a possible commencement is part of the mini-budget process,'' Mr Campbell said.

Macquarie Fields MP Andrew McDonald said he was unaware of Mr Campbell's committee answers but repeated his statement that if the rail link and Glenfield station upgrade didn't go ahead by the next election, Labor's chances of holding onto Macquarie Fields ``would be shot''.

``My electability is dependent on the South West Rail Link and Glenfield station,'' he said.

``It's the issue that most people have to live with day to day and the linchpin on whether I sink or swim.''

Camden MP Geoff Corrigan said that he, Dr McDonald and Liverpool MP Paul Lynch met representatives from the Premier's office last week to put forward their case for the rail link to go ahead.