First-term Pittwater MP Rory Amon - who was also a party spokesman on youth issues - was arrested on Friday morning at Manly Police Station and charged with 10 offences.
They include five counts of sexual intercourse with a person over 10 and under 14, two of attempting sexual intercourse with a child over 10 under 14, two of indecently assaulting a person under 16 and one of committing an act of indecency with a person under 16.
Amon denied the 2017 allegations in a statement, stating he would "make my case in the courts, not in the media".
State Liberals moved swiftly after news of the charges became public on Friday, with Opposition Leader Mark Speakman demanding Amon's resignation from the party and parliament.
Opposition Leader Mark Speakman (pictured) immediately demanded Amon's resignation. (Bianca De Marchi/AAP PHOTOS)
The 35-year-old immediately quit the party and tendered his resignation as an MP to the parliament's speaker.
"The people of Pittwater should have a representative who can dedicate one hundred per cent of their time advocating for this wonderful community," Amon said in his statement.
"As I defend myself against these charges, I will not be able to devote my full energy to representing them."
Detectives started an investigation in June 2022 after reports of a sexual assault in Mona Vale, which is within Amon's electorate on Sydney's northern beaches, five years earlier.
They were told a teenage boy had been abused by a man known to him.
A strike force was set up in March 2023, the same month the state election took place.
The charges relate to offences allegedly committed in June and July 2017.
Amon's matter returns to Downing Centre Local Court in late October but he has been excused from appearing if legally represented.
A police strike force was set up in March last year, the same month as the 2023 NSW election. (James Gourley/AAP PHOTOS)
He was earlier granted police bail with strict conditions.
However lawyers for the MP fronted Manly Local Court on Friday after lodging an application to have his identity suppressed, a bid they later abandoned.
Mr Speakman said the charges made Amon's position in parliament untenable as he would devote time to defending himself instead of serving his constituents.
"The charges laid against Rory Amon are extremely serious … the alleged conduct strikes at the heart of the standards expected of MPs," the Liberal leader said.
"While Mr Amon is entitled to the presumption of innocence, a criminal trial will be some time away and in the meantime the citizens of Pittwater are entitled to have a member of parliament who can discharge their duties in the community fully."
Amon had been quick to rise in the Liberal party and was immediately placed in Mr Speakman's leadership team after his election.
His posts included stints as shadow assistant minister for youth, infrastructure, and transport and roads.
He narrowly scraped over the line to win the northern Sydney seat - long coveted by the Liberals - beating teal challenger Jacqui Scruby with just over 50 cent of the two-party preferred vote.
He served as a Northern Beaches councillor between 2017 and 2023 before entering state politics.
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