Construction of the £395 million Aberdeen bypass could be delayed by as long as two years following a legal challenge against the project.
Campaign group Road Sense said it had instructed its lawyers to challenge a decision by Scottish Ministers to approve the new 46km dual carriageway.
The group said it had identified a number of grounds for their legal challenge, including Scottish Ministers’ decision to restrict the scope and remit of the AWPR public local inquiry and violation of the European Habitats Directive.
It said it would release more detailed information on their legal challenge once its papers had been lodged with the Court of Session in Edinburgh.
The case, however, could take up to 18 months to be heard, raising concerns the project could suffer significant delays.
The scheme had been expected to be procured this year, with construction to begin in 2011.