A North East tennis coach who abused seven girls aged as young as 11 remains in custody ahead of sentencing at the end of this month.

Geoffrey Douglas Hollow, 70, abused the girls over more than a decade while a coach of the Bright and Mount Beauty tennis clubs.

He appeared in Wodonga County Court last week and pleaded guilty to 12 child abuse related charges.

The court heard the offending involved the girls being touched inappropriately, undergoing sexual massages on a modified chair behind locked doors and being asked to wear revealing shorts without underwear.

The offending came to an end in late 2022 when one girl reported her abuse to her mother, with police alerted.

Hollow was arrested by Wangaratta sex offence detectives at his Wandiligong home in 2022, with hundreds of photographs and videos, including of the victims, found on his phone.

He was aged in his 50s and 60s during the offending.

Several victims were in court last week to see Hollow admit to his offending, with many having provided victim impact statements.

Hollow moved from the region when the offending was discovered and wrote a letter of apology to the victims, which was aired in court.

Prosecutor David O'Doherty said there was no explanation for why Hollow had offended, and said he had lived a "Jekyll and Hyde" life.

Hollow remains in custody and is to be sentenced at the end of the month.

He will be a registered sex offender for the rest of his life.