The authority said it is unable to attend the event organised by Shrewsbury Civic Society on November 30 to avoid any form of pre-determination.
Council officers had been invited to take part in the event and answer questions from the public.
Mark Barrow, Shropshire Council’s director of place, said: “The council is planning to submit a planning application in April 2020, and therefore we have to be very careful to avoid what could be interpreted as any form of pre-determination.
“We will be undertaking our pre-planning stakeholder and public consultation events week commencing 20 January 2020 for six weeks, and Shrewsbury Civic Society will be invited to a one on one meeting as part of this. The planning application will then be submitted in April 2020, incorporating feedback from this consultation process.”
Shropshire Wildlife Trust, one of the organisations against the road, said it is disappointing there will be an empty seat where a council representative was due to be sat.
Robin Mager, the trust's planning officer, said: “Given Shropshire Council’s public statements on the road so far it seems a little late in the day to be worried about accusations of pre-determination. They have initiated, designed and promoted the scheme from day one so it's hard to see how they can claim that they haven't already decided that it's a good idea."
He said it would have been an ideal opportunity for the council to address concerns from environmental groups.
“How can a body willing to spend a minimum of £84 million of public money refuse to take part in a well-organised debate hosted by Shrewsbury Civic Society?" Mr Mager added.
"This smacks of hypocrisy and a council running scared. We want to see a comprehensive plan that addresses the transport concerns of Shrewsbury's residents whilst protecting the local environment and addressing the climate emergency. The council is giving us lots of warm words about these issues but no firm commitments."
Shropshire Wildlife Trust says it is opposed to the road because of the damage it would cause to wildlife habitats, the inevitable new housing development in areas opened up by the road and the increased carbon footprint of construction and more vehicles.