Mr Brewer said an operating loss of $139,136 for the trams' first eight months had prompted a request from the waterfront agency for a $150,000 council subsidy.
The council had also included $8.2 million in the first year of its draft long-term budget for an extension of tramlines across Viaduct Harbour.
"Let's not forget that this is a project that Waterfront Auckland promised ratepayers would pay for itself," Mr Brewer said.
"However, as many of us predicted, their forecasting of how many people would pay good money to circumnavigate a carpark was always pie in the sky.
"It seems crazy that while existing trams are losing money hand over fist and are so poorly patronised, ratepayers are now being asked to spend millions more extending the project."
But Mr Lee accused Mr Brewer of showing a similar lack of vision to those conservative politicians responsible for ripping up the city's successful tramlines in 1956.
Mr Lee, a qualified tram driver, said the existing circuit was "remarkably successful" and would be more so once it could be extended to the Maritime Museum and beyond.
"It's a small peg in the ground. It has been brilliant for creating a sense of place and a wonderful ambience in the Wynyard Quarter - it's absolutely magic."
He said the post-cup period, compounded by a wet summer, had been difficult for retailers as well "but does that mean we should shut all the shops down in Auckland?"
"Yes, it needs a subsidy, but tell me what transport in Auckland doesn't.
"It tailed off over an extremely bad summer but what we are looking at now is much more sustainable support coming, particularly from schools and inbound tourist groups."
Waterfront Auckland chief executive John Dalzell said the tram circuit was one component of a "total package" that was shaping up as a highly successful development project.
"But as soon as you try to cherry-pick or take things out because you don't think they are contributing, you destroy what you've created down there."
