A day after the National Rifle Association filed a lawsuit saying its reputation had been smeared by its most prominent contractor, that contractor claimed in its own filing that it had been smeared by the N.R.A.

The dueling claims escalated the legal battle between the N.R.A. and Ackerman McQueen, an advertising firm that has worked with the gun group for nearly four decades. The bitter split between the organizations sparked a recent power struggle between Wayne LaPierre, the N.R.A.’s chief executive, and Oliver North, an Ackerman employee who was ousted as the N.R.A.’s president last month.

Ackerman is seeking $50 million in the counterclaim it brought on Thursday in state court in Virginia, a filing that was previously reported by The Daily Beast. The N.R.A., in two separate suits against Ackerman, had accused it of refusing to fully cooperate with an audit, defaming Mr. LaPierre and breaching confidentiality agreements.

Ackerman rebutted those allegations in its suit, saying that it had “complied with every audit” requested by the N.R.A. — including one in February — and that it itself was defamed by the gun group.