The opinion
—Order, Supreme Court, New York County (Eileen Bransten, J.), entered on or about March 25, 1998, which, inter alia, denied defendant’s motion for rejection of a Referee’s report to the extent that the Referee recommended dismissal of the action, denied defendant’s motion for leave to amend his answer to assert counterclaims for divorce and confirmed the Referee’s report and dismissed the action, unanimously affirmed, without costs.
Even if we were to find that defendant’s proposed counterclaim validly set forth a cause of action for divorce on the ground of cruel and inhuman treatment (see, Smith v Smith, 206 AD2d 255 , lv dismissed 84 NY2d 977 ) or of constructive abandonment (see, George M. v Mary Ann M., 171 AD2d 651 ), we would nonetheless agree with the motion court that amend *468 ment of the answer after the completed trial of plaintiffs predicate claim of constructive abandonment before the Referee would unjustifiably prejudice plaintiff by belatedly introducing an entirely new theory into the case (see, Symbax, Inc. v Bingaman, 219 AD2d 552, 553 ). Denial of leave to amend under these unusual circumstances was proper (see, supra). We have considered defendant’s remaining arguments and find them to be unavailing. Concur — Sullivan, J. P., Lerner, Rubin and Tom, JJ.