Prosecutors on Wednesday sought to adjourn the man's court case for one week to prepare the fresh charges.

They said a further four people had made sexual abuse complaints against the man in recent months, however did not publicly reveal the nature and details of the allegations.

Police documents previously sighted by the Mercury, outline in horrific detail what police will allege was the man's systemic abuse of his step-daughter between 1983 and 1993, and his step-granddaughter from 2008 to 2014.

The step-daughter claims she was repeatedly raped by her step-father from the age of seven.

She said the abuse occurred "every second day or so", usually when she was alone in the house with him, but claimed that her mother had witnessed one of the assaults.

She said she reported the abuse to police in 1991 at the age of 14 and her step-father was arrested, interviewed and charged.

However, the step-daughter said her mother kicked her out of home as punishment for telling the police and would not allow her back into the house until she told detectives she'd lied.

"The [victim] states she was 14 years old, homeless and desperate, with no support, so she did as her mother suggested and told police she'd made up the allegations," court documents said.

It is alleged the assaults continued after the girl returned home and only stopped when she was about 16.

The girl subsequently had children of her own.

In 2008, the girl, her partner, and their children moved in with her mother and step-father.

It is alleged the step-father then began molesting his step-granddaughter.

When the step-granddaughter eventually spoke to police in 2019, she said her step-grandfather would touch her "whenever he could".

He also allegedly supplied her with a "bong" to smoke when she was at his house one day with her older sister.

She recalled being in Year 2 at the time.

The man was arrested in August 2019.

He denied the allegations, labelling them "ridiculous".

The case returns to court next Wednesday.