BOSTON - A class action lawsuit has been filed against the Massachusetts Turnpike Authority over the discount users of the Fast Lane electronic toll paying system get that E-ZPass users do not.

The suit charges that offering the discount to one group of toll payers but not the other violates Constitutional protections of interstate commerce.

Plaintiffs attorney Matthew Pawa told The Boston Globe that the Turnpike can't charge more for interstate tranactions on E-ZPass - which is used around the Northeast, including Maine - than it does for transactions in Massachusetts' intrastate Fast Lane program.

He said the suit could involve thousands of people and millions of dollars in damages.

The Turnpike Authority declined comment.

About a third of electronic toll users on the Mass Pike use E-ZPass.