Transport Minster Steven Joyce does not believe extending Auckland's rail link across the Waitemata Harbour into the North Shore is affordable.
An independent survey has found that many Aucklanders want a rail service on a new Waitemata Harbour crossing and the Transport Agency has released a report evaluating various options.
The UMR Research poll released on Monday found 79% of 241 people surveyed think that train tracks should be installed on the new crossing, whichever form it takes.
A tunnel is favoured by 41% of those surveyed, while 38% want a new bridge and 12% do not want either. The survey had a margin of error of plus or minus 6.3%.
However, Mr Joyce on Tuesday was sceptical at the idea of a rail link, saying it is amazing how generous people can be with other people's money.
"The only rough costing I have seen for this is in the order of $3 billion to cross the harbour to get to Takapuna, plus another $6 to $7 billion to get it up through to Albany.
"A lot of things sound like really good ideas when we have no idea what they will cost us."
However, Auckland Council's transport committee is refusing to enter a debate with Mr Joyce over the issue.
The committee on Tuesday considered a Transport Agency report evaluating the options of a new bridge, a tunnel and rail link and voted to seek feedback from the public.
Chairperson Mike Lee said the debate he believes Mr Joyce intended to spark is premature, given the region's other transport priorities.
Mr Lee also questioned how up-to-date the report could be with tunneling techniques rapidly developing and construction about 20 years away.
Auckland Mayor Len Brown has said he supports a rail link to the North Shore.