Dawson is already facing a murder charge over the disappearance of his then-wife Lynette in Bayview in 1982.

The 70-year-old pleaded not guilty to the murder charge in the Downing Centre Local Court on Thursday morning.

The former Cromer High School teacher then attended Surry Hills Police Station at midday and was charged with having carnal knowledge of a girl between the ages of 10 and 17.

The disappearance of Dawson's former-wife became the subject of journalist Hedley Thomas' internationally successful podcast, The Teacher's Pet, which was published by The Australian newspaper.

The podcast also revealed allegations of sexual assaults and student-teacher relationships at high schools on Sydney's Northern Beaches in the 1970s and 1980s.

It is alleged he engaged in carnal knowledge with a former female student in 1980, when she was 16 years old.

Detective Superintendent John Kerlatec said the charge came after an "exhaustive investigation" by a specialised strike force.

"It's a very serious charge, it does relate to a 1980 charge, hence the term 'carnal knowledge', I will add that this investigation is continuing," he told reporters in Sydney.

"Any other victim or any other person who has any other information we encourage them to come forward."

Dawson was granted conditional bail for the carnal knowledge charge and ordered to front Downing Centre Local Court on August 8.

Australian Associated Press