By Dave Warner

NORRISTOWN, Pa (Reuters) - A commissioner from Philadelphia's largest suburban county was arrested on Tuesday and charged with lying about business relationships with a contractor, the local district attorney said.

Montgomery County Commission Chairman James Matthews was charged with perjury and false swearing, according to a statement issued by the district attorney's office.

The charges stem from an 18-month grand jury investigation examining evidence about alleged nonpublic meetings held between Matthews and Commissioner Joseph Hoeffel outside the presence of the third commissioner, Bruce Castor, it said.

According to the statement by Montgomery County District Attorney Risa Vetri Ferman, the grand jury found Matthews lied on several occasions during his sworn testimony about a business relationship with a company contracted to do title work.

"Matthews lied with such ease and frequency, that he acted as though, as Chairman of the Montgomery County Board of Commissioners, he is above the law," the grand jury report said.

A three-person commission governs county business. Matthews and Castor are Republicans, and Hoeffel is a Democrat.

Matthews was expected to be arraigned later on Tuesday.

(Writing by Lauren Keiper; Editing by Ellen Wulfhorst and Greg McCune)