Auckland Central MP Nikki Kaye denies trying to hitch an electioneering ride back to Parliament on an ambitious tramway proposal, saying she started work on it last year.

A plan she's pushing for a tram loop from the waterfront to Ponsonby and Grey Lynn has drawn sceptical responses from Auckland Council transport chairman Mike Lee and the Labour candidate for her seat, Jacinda Ardern.

They've questioned her sincerity, saying she's part of a Government that's squeezed public transport spending and refused to support the $2.4 billion central city rail tunnel project.

But Ms Kaye said yesterday she believed the projects were complementary and necessary to keep up with rapid urban growth, although a tramway could be built much faster and for far less money than the rail tunnel.

She hoped the tram proposal could be promoted across party-political lines and produced a letter showing she'd referred an early version of it in July last year to former Auckland Transition Agency head Mark Ford, who now chairs Auckland Transport.

That version, drafted by Western Bays community advocate and actor Geoff Houtman, was also presented to the former Auckland City Council.

Mr Houtman said yesterday the 6.2-kilometre tramline through Ponsonby and Grey Lynn to the Museum of Transport and Technology's tramway should cost $26 million.

Ms Kaye's proposal is more ambitious, involving much of the same route but deviating around Richmond Rd and Great North Rd before looping down Queen St to Britomart and the waterfront. She has written to Auckland Mayor Len Brown and Transport Agency northern director Stephen Town asking them to consider a joint feasibility study into the idea.

She told the Herald although she supported the CBD rail link, she didn't believe congestion in the fast-growing Western Bays suburbs could wait seven years for it to be built.

Mr Brown's office said he'd consider the request after returning to work on Monday, from Europe, and Mr Town indicated the Transport Agency would take its lead from Auckland Transport.

Ms Ardern said it was hard to believe her opponent supported the rail tunnel when she was part of a Government arguing there was still room for more buses and cars on city streets.