An alternative plan for the Cross Tay Link Road could delay the project by 17 months and cost taxpayers an extra £8 million, councillors will be warned next week.
The proposed route, which was backed by First Minister Nicola Sturgeon at the start of the year, will link the A9 over the River Tay to the A93 and A94 north of Scone.
The aim is to cut down on congestion in the city centre and reduce alarmingly high levels of air pollution.
However, concerns were raised this summer that the preferred route for the £113 million scheme will run directly through a new 700-house estate to the north of Scone.
Scone and District Community Council (SDCC) pushed for an alternative lay-out after receiving support from local people in a survey carried out over the winter months.
The watchdog group recommended moving the new road further north to avoid running it through the new housing development and causing potential health and pollution problems for people living there.
Next week, councillors will be urged to back the original. preferred design which was formally backed under the previous SNP administration late in 2o16.
A joint report by roads infrastructure manager Jillian Ferguson and council solicitor Debbie Robertson outlines several reasons why the alternative plan – known as the Northern Route – should not be supported.
It followed a four-month review of the new design.
They say it would cause delays to the project by 17 months and would need at least £7.1 million of additional capital funding.
This will increase further for every month the scheme is delayed due to construction inflation,” the report states.
Councillors will be told delaying the project could also jeopardise £8.5 million match funding from Sustrans.
There are also concerns the local authority would be forced to create a “low emission zone” in the city centre that would involve significant traffic restrictions.
Officers further argued that a delay would cause “reputational damage” for the council, with “negative press coverage” leading to a “poor public image”.
The report concludes: “The council has responded to the concerns that have been raised by the SDCC by commissioning a technical comparative assessment of an alternative northern route… and by instructing internal and external legal advice.
“This process has been resource intensive and required considerable additional expenditure.”
It states: “Overall, the conclusions that are set out in the assessment do not support the adoption of the northern route. Indeed, the technical comparative assessment favours the current preferred route.”
The community council has asked to address councillors at Wednesday’s meeting. Chairwoman Vanessa Shand said: “The report comes up with several conclusions, but there is no evidence there to back them up.”
She said: “We are very concerned about this road going past houses in the Scone North development. This could be a real health hazard for people living there.”