Teen singer/actress Hilary Duff's mother is being sued for breach of contract by a Canadian clothing firm, alleging Susan Duff violated an exclusive merchandising deal for her daughter's fashion line.

NTD Apparel filed a multi-million dollar lawsuit in Los Angeles Superior Court this week (ends04NOV05), claiming Susan had performed "unlawful, unfair and deceptive business practices" while agreeing sales deals for the CHEAPER BY THE DOZEN star's Stuff By Hilary Duff range.

The suit also names the family's entertainment company Rafter H as a defendant, alleging they violated an exclusive merchandising agreement with NTD by agreeing side deals with rival retail firms.

In response, Rafter H told the New York Daily News the suit was "without merit" and are planning to sue NTD for using low-quality goods in the Stuff collection.