Key Points:

Finance Minister Michael Cullen is shrugging off questions about the future of railways after hinting Labour is considering re-nationalising the operation of the trains run by Toll Holdings.

National deputy leader Bill English said the Government had confirmed it was considering the option of a purchase and would have held discussion on the matter.

Cullen's threat follows four years years of disagreement about the wording and obligations of the rail access agreement negotiated between Treasury and Toll Holdings, the Australian-owned company which operates the trains.

The agreement sets terms and obligations between Toll and Ontrack, the state owned enterprise that owns the tracks. With both claiming they are not making a commercial return, the row has come to a crunch.

Cullen refused to comment on what he said was a confidential commercial negotiation, but his office confirmed that all options including a purchase remained on the table.

English said there was a view within Ontrack that the operation of the trains under Toll ownership should be handled by Ontrack.

It is also understood that Toll has been seeking to resolve the disagreement over operating obligations by obtaining a taxpayer subsidy.

Ontrack board members include Labour party president Mike Williams and former Labour Cabinet minister Clive Matthewson.

Toll Holdings chief Paul Little said on Monday: "We've been in discussions for quite some time about access to the track and charges that will be levied on us, and certain undertakings that were made at the time we did the original transaction."

Toll Holdings shares closed down 24c at A$13.34 yesterday on the ASX.