A former minister in Australia's New South Wales (NSW) state government has been charged with sexually abusing a man and a teenage boy.

Gareth Ward - now an independent MP - is alleged by police to have committed the crimes in 2013 and 2015.

Mr Ward, 40, denies the charges.

"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 on Tuesday.

Mr Ward has been accused of five charges in total. The most serious - one charge of sexual intercourse without consent - carries a maximum jail term of 14 years.

"Police will allege in court that the man indecently assaulted a 17-year-old boy at [NSW suburb] Meroo Meadow in February 2013, and sexually abused a 27-year-old man in Sydney in September 2015," NSW Police said in statement, without giving further details.

Mr Ward revealed he was being investigated by police last year, prompting him to resign as minister for families, communities and disability services. He also stopped sitting with the ruling Liberal Party in parliament.

On Tuesday, NSW Premier Dominic Perrottet said he would move a motion to remove Mr Ward from parliament if he did not resign.

Mr Ward should be presumed innocent but it was "not compatible with the seriousness of the charges" for him to remain as an MP, the premier said.

Mr Ward is due to face a court in May.