Everett and its firefighters union remain locked in a contentious contract dispute more than a month after the city admitted it violated state labor laws in the negotiation process.

The state Department of Labor Relations is reviewing a new allegation by the union that the city violated the law when it unilaterally increased union members’ pay by 1.5 percent on Dec. 6. A division investigator has scheduled a Feb. 13 hearing , ­according to Craig Hardy, president of Local 143 of the International Association of Fire Fighters.