—Judgment, Supreme Court, New York County (Harold Tompkins, J.), rendered March 14, 1996, convicting defendant, after a jury trial, of criminal sale of a controlled substance in the third degree, and sentencing her, as a second felony offender, to a term of 7V2 to 15 years, reversed, on the law, and the matter remanded for a new trial.
Defendant was arrested on August 18, 1995 based on her participation with another in the sale of crack cocaine to an undercover officer. The transaction took place in a park located at 27th Street and 2nd Avenue and was observed by a ghost officer. Defendant was arrested shortly after the sale, and was subsequently identified by the undercover officer. The codefendant was arrested while attempting to leave the park, and the police recovered more narcotics and prerecorded buy money from him.
At trial, defendant called Linda Trafton as a defense witness. Trafton testified that she and defendant had been drinking together in the park since the previous day, and that at no time did she observe defendant sell drugs. On cross-examination, the prosecutor asked Trafton whether she had ever gone by the name ‘Williams”, to which Trafton responded negatively. The prosecutor then asked Trafton whether she had ever engaged in prostitution near the park where defendant was arrested, and she responded “no.” Next, with a long “rap sheet” in his hand, the prosecutor asked Trafton whether she had used 13 specific aliases and Trafton responded no to each one.
At a sidebar, defense counsel requested an offer of proof from the prosecutor demonstrating that the rap sheet (which “accidentally” fell to the floor during the prosecutor’s cross-*142examination) actually was Trafton’s. Defense counsel noted that the name on the rap sheet was “Linda Williams” not “Linda Trafton.” The prosecutor made the following representations in an attempt to establish a good-faith basis for the questioning: that a criminal records check regarding “Linda Trafton” did not yield any results; that he believed that Trafton had identified herself as “Linda Ann Christina Williams Trafton” when she was sworn in as a witness; that the rap sheet for “Linda Williams” revealed a woman whose race and age matched Trafton’s, and that Linda Williams had been arrested for numerous prostitution offenses in precisely the same area as defendant’s arrest and Trafton’s residence; and lastly, that defendant herself had a prior arrest for prostitution during which she used the street name “Mercedes”, and Trafton had used that name in referring to defendant during the trial. These facts caused the prosecutor to conclude that Trafton and defendant “may know each other through the profession of prostitution.”
Upon defense counsel’s request, the court asked the stenographer to check her notes, which revealed that Trafton had not used the name Williams when she was sworn in. The prosecutor then conceded that he was mistaken and told the court that he would not oppose a jury instruction advising the jury that the rap sheet was not evidence. However, the prosecutor opposed any charge instructing the jury to disregard the questions related to the rap sheet because, in his view, he had a good-faith basis to ask them. Over defense counsel’s vehement objection, including a motion for a mistrial, the court told the jury that the sheet on the prosecutor’s desk “was not evidence,” but declined to instruct them any further.
On appeal, defendant claims that the court’s refusal of his request for a curative instruction regarding the improper cross-examination of a defense witness deprived her of a fair trial. We agree. “A witness may be interrogated upon cross-examination with respect to any immoral, vicious or criminal act * * * which may affect [her] character and show [her] to be unworthy of belief, provided the cross-examiner questions in good faith and upon a reasonable basis in fact” (People v Simpson, 109 AD2d 461, 464, appeal dismissed 67 NY2d 1026, citing Richardson, Evidence § 498 [Prince 10th ed]; see also, People v Greer, 42 NY2d 170, 176; People v Schwartzman, 24 NY2d 241, 244, cert denied 396 US 846; People v Alamo, 23 NY2d 630, cert denied 396 US 879). Of course, the nature and scope of such questioning is best left to the sound discretion of the trial court, and will not be disturbed on appeal absent an abuse *143of such discretion (People v Schwartzman, supra; People v Simpson, supra).
Where a prosecutor fails to demonstrate a good-faith basis for the questioning, or that the allegations have a reasonable basis in fact, it is error for a trial court to permit such questioning or to refuse to strike it from the jury’s consideration (see, People v Colas, 206 AD2d 183, 188, lv denied 85 NY2d 907; People v Liriano, 173 AD2d 489; People v Simpson, supra; People v Huntley, 87 AD2d 488, 495, affd 59 NY2d 868). While the cross-examination in the present case involved a defense witness rather than the defendant herself, the same rule obtains if the witness’s testimony is material to the defendant’s guilt or innocence (see, People v Torriente, 131 AD2d 793, 793-794; see also, People v Lediard, 80 AD2d 237, 242). Here, the testimony of Traffcon was unquestionably material since it was in the nature of alibi testimony.
The record demonstrates that the prosecutor’s questioning of Traffcon regarding her alleged history of prostitution lacked a reasonable basis in fact (People v Colas, supra; People v Liriano, supra; People v Simpson, supra). The underlying premise of the prosecutor’s claimed good-faith basis, to wit, Traffcon’s use of the name Williams when she was sworn in as a witness, proved to be completely erroneous. Moreover, the additional reasons given by the prosecutor amounted to nothing more than a hunch that Traffcon might be the person named in the rap sheet. The cross-examination of a witness regarding inflammatory allegations of prior immoral and criminal activity cannot be based on so flimsy a predicate (People v Alamo, supra, at 633 [good-faith questioning requires that the questioner have “some reasonable basis for believing the truth of things he was asking about”]). This error was compounded by the court’s inexplicable refusal to instruct the jury to disregard the improper questioning (see, People v Liriano, supra). These were groundless accusations, as the prosecutor conceded, and should have been stricken regardless of the prosecutor’s subjective assertion that the questions were asked in good faith. It is disturbing to us that a trial court, having observed that a witness’s reputation was impugned by false and scurrilous allegations, would refuse to rectify the situation when given the opportunity. Proper ameliorative action by the trial court might have cured any error resulting from the questioning.
The error was not harmless. Although strong evidence of defendant’s guilt existed, the prosecutor’s negligent and misleading cross-examination of Traffcon destroyed any chance that the jury would believe the alibi-type defense (People v *144Liriano, supra; People v Delacruz, 127 AD2d 887). The case came down to a credibility contest between Trafton and the two police officers who claimed to witness defendant’s participation in a drug sale. Defendant’s hope of winning this credibility contest was dashed when the prosecutor’s baseless accusations suggested to the jury both that Trafton was a prostitute and that she was a liar for denying that history (see, People v Simpson, supra [while prosecutor may continue to cross-examine witness about prior bad acts in an attempt to persuade witness to change testimony, it is improper to use innuendo and suggestion to persuade jury to disbelieve the witness’s denial]). We find this fundamental error to be harmful without regard to the quantum of evidence at trial (People v Crimmins, 36 NY2d 230, 240, n; see also, People v Savvides, 1 NY2d 554; cf., People v Schwartzman, supra). Concur — Milonas, J. P., Rosenberger, Wallach and Mazzarelli, JJ.