The call for a Norfolk council to get behind the Norwich Western Link has been branded "naive and premature" by Liberal Democrats.
Gerard Mancini-Boyle, deputy leader of North Norfolk District Council's (NNDC) opposition Conservative group, tabled a motion backing the county council's plans for the controversial £198m road.
But the majority of the Liberal Democrat administration rejected the motion, saying there are too many unknown variables.
The road would provide a link between the NDR (Broadland Northway) and the A47 southern bypass - but significant opposition has arisen due to its feared environmental impact and doubts over the feasibility of the project.
The motion put to NNDC's meeting on Wednesday asked the authority to "pledge its full support for the construction of the Norwich Western Link dual carriageway".
Mr Mancini-Boyle called for politics to be put aside and said anyone who does not support the road is guilty of "reverse NIMBYism", arguing people near the road support it.
He also argued the road would help cut travelling times for ambulances.
Lucy Shires, cabinet member for organisation resources, said it was unfair to suggest the road would have a meaningful impact.
She said: "The longest response time I’ve seen in the data is 21 hours and 57 minutes - there is nothing this road will do to change that.
“We have an underfunded system and I’m sick of hearing sob stories from across the chamber to try to pluck at the heartstrings of people when we have got hard-working NHS staff that are struggling. It is not fair.”
Worstead councillor, Saul Penfold, called the motion "naive and premature" arguing it would be irresponsible to support the road at this stage.
"It asks not for an in-principle support of the road but for a full pledge for its construction.
“It asks us to do this when the county council and its cabinet do not even know what those construction costs will be nor does it know the timetable for completion.”
Tom Fitzpatrick, Conservative councillor for Walsingham and a cabinet member at the county council, said the road has been supported by Lib Dems at South Norfolk and Broadland and called for North Norfolk's to do the same.
He said: "Do the right thing, let's do it for the good of north Norfolk, supporting existing jobs."
The motion was rejected.
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