West Auckland politicians are worried that a $160 million railway trench being dug through New Lynn will be left as a gaping hole because no money will be available to build a covered station inside it.

The Waitakere City Council and the Labour MP for New Lynn, David Cunliffe, want the Government to tell their constituents whether it will plug a $13.6 million funding gap left by its cancellation of a regional fuel tax.

Waitakere Deputy Mayor Penny Hulse, whose council is contributing $20 million to the trench and $48 million to associated developments costing $144 million for the transformation of New Lynn's town centre, said yesterday that the whole project risked unravelling at the last hurdle.

Without $13.56 million from the Auckland Regional Council for a partly covered station, to become part of a bus-rail interchange, the Government's investment in the 1.1km trench would be seriously undermined.

"A bare bones station of concrete stairs down to the platforms just won't cut it," she said.

"We want people to use the train, but they're not going to stand in the rain in a trench and use the train."

Ms Hulse said 250 workers were digging the rail trench to a depth of up to 8m through New Lynn, and developers were lining up to build retail and residential projects close by, in line with the regional growth strategy of intensification around key transport hubs.

She said her council "absolutely applauded" the Government for continuing with rail electrification, but urged it to make the best of the investment.

If it did not see reason in ensuring enough funds for "the last piece of the puzzle", the regional council should be prepared to borrow money to protect the integrity of its growth strategy.

Mr Cunliffe, who helped to persuade former Finance Minister Michael Cullen to open the previous Government's chequebook for the trench by pointing out potential traffic chaos around New Lynn's rail-road roundabout, said a well-designed station was essential to the town's redevelopment.

"This is a classic case of a major transformational investment project that's unleashing hopefully hundreds of millions of dollars of private co-investment, but absolutely central to it is a getting good station infrastructure to set the tone for the development.

"If we are left with a huge hole in the ground that draws defeat from the jaws of victory on what was looking like a fantastic project, I will be reminding the public of this disgrace for the next three years."

Transport Minister Steven Joyce would give no assurances about New Lynn, but said Mr Cunliffe should give the Government and its officials time to work through Auckland's list of unfunded public transport projects with regional representatives.

"He's well ahead of himself and needs to take a deep breath."

Mr Joyce was unable to say whether the Government would alter a policy it inherited, under which its agencies pay for railway tracks and basic platforms, and the Auckland region foots the bill for all other station structures.

But he believed there was some flexibility within existing funding rules "to ensure that projects under way get completed and balls don't get dropped".

"All I'm saying is we are well aware of the commitments, we're working through the details and we'll work with the ARC."

The Government has already departed substantially from the inherited funding split by promising to pick up Auckland's liability for more than $500 million of new electric trains.

But it has yet to give any guarantees about a $202 million shortfall identified by the regional council for stations, ferry terminals and a new integrated transport ticket.

Big funding gaps for other flagship stations at Newmarket and Manukau, as well as a range of smaller developments, will be examined by the council today at the first of a new round of meetings to write a new budget in light of the Government's decision to scrap the regional fuel tax.