Sexual assault charges against the disgraced film producer’s Harvey Weinstein may proceed, a New York judge ruled on Thursday.

Judge James Burke rejected a motion from Weinstein’s attorneys to dismiss the criminal charges against him.

The ruling is a boon for the prosecution, which has been clouded by allegations that police acted improperly in the investigation that led to Weinstein’s arrest in May.

Weinstein, 66, is charged with raping a woman he knew in a hotel room in March 2013 and forcibly performing oral sex on another woman in 2006 at his Manhattan apartment. He has denied all allegations of non-consensual sex.

There is “no basis for the defendant’s claim of prosecutorial or law enforcement misconduct in the proceedings”, the judge said in a written decision issued after the hearing. He set the next court date for 7 March.

Weinstein’s lawyers had argued the case was “irreparably tainted” by a detective’s alleged coaching of a potential witness and one of the accusers. They also said the grand jury should have been shown evidence that Weinstein had exchanged friendly emails with his two accusers after the alleged attacks.

After the hearing, Weinstein’s lawyer, Benjamin Brafman, said he remained confident the former Hollywood heavy hitter will be “completely exonerated” at trial.

“We intend to vigorously defend this case to the best of our ability,” Brafman said.

Weinstein, wearing a business suit and tie, who remains free on $1m bail, left court without commenting.

Actors Marisa Tomei and Amber Tamblyn were in court on Thursday to show support for the accusers, along with other women supporting the Time’s Up advocacy and legal defense group for sexual assault and harassment survivors and the wider movement known as #MeToo that was revitalized by mass allegations against Weinstein exposed in October 2017.

“Today, here in New York, we saw the first steps towards justice,” the Time’s Up president, Lisa Borders, said after the judge’s ruling. Weinstein had “failed in his efforts to avoid accountability for his crimes”, she said.

Weinstein’s defense was boosted in October this year by back-to-back allegations of misconduct in the police investigation.

The Manhattan district attorney, Cyrus Vance Jr, dropped one of the charges against him – allegations that he raped an aspiring actress who was still in college – after evidence surfaced that Det Nicholas DiGaudio instructed a potential witness to keep some of her doubts about the veracity of the allegations to herself.

DiGaudio allegedly told the witness in February that when she spoke to prosecutors, “less is more”. That witness never testified before the grand jury that indicted Weinstein.

Prosecutors also disclosed an allegation that DiGaudio urged the 2013 rape accuser to delete private material from her cellphones before handing them over to the district attorney’s office.

But the district attorney’s office said the material did not pertain to Weinstein and she did not actually delete anything.

Attorney Gloria Allred, who represents one of the accusers, said there is “still time for other accusers to come forward” in the criminal case.

She encouraged anyone who might have relevant evidence to report it.