A former Federal Court judge is investigating possible legal action against the Napthine government over concerns it has provided misleading information on the east-west link tunnel.

Ron Merkel, QC, and law firm Maurice Blackburn are considering whether the state government has engaged in misleading and deceptive conduct in relation to its secretive business case for the $6 billion to $8 billion road project.

They are working on a pro bono basis with local group Residents Against the Tunnel (RATs), which announced the possibility of a legal challenge at a community meeting on Sunday.

It is understood the legal team could argue the Coalition has breached national competition laws by presenting a business case that is fundamentally flawed and misleading.