National's Northcote candidate Jonathan Coleman questions the feasibility of SkyPath, saying the New Zealand Transport Agency will need to make a decision on whether the Auckland Harbour Bridge's clip-on lanes could support it.

Coleman made the surprise comment in a head-to-head debate with Northcote's Labour candidate Shanan Halbert, livestreamed by the North Shore Times on Tuesday.

Coleman questioned whether construction company Downer had withdrawn from the public-private partnership for financial reasons, or because SkyPath isn't viable.

Supplied National's Northcote candidate Jonathan Coleman raises questions about the viability of SkyPath in a head-to-head candidates' debate with Labour's Shanan Halbert.

If it could be done structurally, it would have to link to the proposed coastal cycleway, SeaPath, so it didn't bring 8000 visitors a day, at peak times, into Northcote Pt, which would destroy the suburb, Coleman said.

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It would then have to compete for funding under the Urban Cycleway Plan, but would stand a good chance.

Coleman saw both roads and increased use of ferries as solutions to Northcote's congestion.

Halbert said National had made no clear commitment to SkyPath and pointed to Labour's pledge of $30 million funding for SkyPath.

Halbert said it was only Coleman's Northcote Pt neighbours, on Auckland's North Shore, who opposed it. Residents need to realise they live on a public road, he said.

Halbert commutes to Māngere daily and also supports the good work that has been done by the T3 lane, with 70 per cent of commuters down Onewa Rd using public transport.

Labour sees public transport as the solution and would bring in a rapid transit network, across the Shore, including light rail to Takapuna by 2030, Halbert said. He couldn't answer questions about Labour's plans for an additional harbour crossing, however.

Coleman says, as MP, he would advocate to bring an additional harbour crossing forward.

The pair disagreed on whether 400 of the 1200 new state houses being build in a Northcote development should be sold on the open market, as National plans to.

Halbert would like to see them kept as affordable houses long-term, with owners selling them back to the Government after five years, so they stay as affordable.