The 40-year-old was charged on Tuesday with three counts of assault with an act of indecency, and one count each of sexual intercourse without consent and common assault.

NSW Police allege he indecently assaulted a 17-year-old boy at Meroo Meadow in February 2013, and sexually abused a 27-year-old man in Sydney in September 2015.

Premier Dominic Perrottet, who is on paternity leave, immediately called for Mr Ward to resign from parliament, saying he will take steps to remove him unless he does.

"While Mr Ward is entitled to the presumption of innocence, as any citizen is, the standards expected of an elected member of parliament are not compatible with the seriousness of the charges he is facing," the premier said in a statement.

"Following discussion with the acting premier, I have therefore attempted to contact the Kiama MP to seek his resignation from the parliament with immediate effect.

"Should Mr Ward not resign, the government will move a motion to remove him from the parliament."

Mr Ward's resignation or forced exit would trigger a by-election in the seat of Kiama, and a loss would further weaken the position of the Perrottet minority government.

The premier said the charges came after an extensive investigation by police and a review of the matter by the Department of Public Prosecutions.

Mr Perrottet said he had also written to the state director of the Liberal Party to ask for Mr Ward to be suspended until an outcome is reached.

"Mr Ward is entitled to defend himself against the serious charges against him but he must do that as a private citizen."

Opposition Leader Chris Minns asked acting premier Paul Toole to confirm Mr Ward would be expelled from parliament during question time on Tuesday.

"The premier and I have had a discussion to today and we have asked (the member for Kiama) to resign from the parliament," Mr Toole said.

Mr Toole said the premier had not yet been able to speak with Mr Ward.

Strike Force Condello was established in May to investigate allegations of sexual violence committed by the Kiama MP, which included NSW detectives from the State Crime Command's Child Abuse and Sex Crimes Squad.

Mr Minns said Labor would support a motion to expel Mr Ward from the parliament if it was brought forward.

"Clearly, the position of the member for Kiama is completely untenable, given the serious nature of the charges levelled against him," he said.

Labor will continue to "ask questions about the circumstances leading up to the establishment of Strike Force Condello last year," Mr Minns said, adding a "series of serious allegations" had been levelled against Mr Ward last year.

"We reserve that right to ask questions in relation to what senior ministers did when that information was known to them over the last six months and prior to the establishment of that task force."

Mr Ward stepped aside as families, communities and disability services minister in May after identifying himself as the politician under investigation for "sexual violence-related offences" dating back eight years.

He also recused himself from the Liberals partyroom and moved to the crossbench, but denied the allegations.

Mr Ward on Tuesday said he was "totally innocent of the charges brought against me" in a statement provided to the ABC.

"I will be instructing my lawyers to seek to bring this matter before the courts as quickly as possible and I look forward to demonstrating my innocence there," he said.

"While others have already attempted to prosecute my case in the media rather than the courts, out of respect for our justice system I will not be doing the same."

Mr Ward was granted conditional bail and will appear at Port Kembla Local Court on May 18.

AAP has contacted Mr Ward for comment.

Australian Associated Press