A man has been charged with the ongoing abuse and grooming of two children on the NSW far north coast.

Child Abuse Squad detectives arrested a 44-year-old man on Monday night following an investigation at Ballina into the suspected abuse of two siblings, a boy and a girl aged under 14, by a family friend.

Police allege the children had been indecently assaulted, sexually abused and groomed on numerous occasions during the past year.

Officers also seized a mobile phone which had an image depicting child abuse.

The man has been charged with seven counts of indecently assaulting a person under 16, four counts of inciting a person under 16 to commit an act of indecency, two counts of grooming a child under 14 for unlawful sexual activity and using a child under 14 to make child abuse material.

He was refused bail to appear at Tweed Heads Local Court on Tuesday.

AAP