The National Prosecuting Authority (NPA) will apply to the Cape High Court on Thursday for leave to appeal a finding that 29 sexual offences are not punishable because the Sexual Offences Act does not specify penalties for them.

"We believe that we will successfully argue for the court to grant us leave," NPA spokesman Mthunzi Mhaga said.

Earlier this month, the court upheld a decision by the Riversdale Magistrate's Court that a man who forcibly fondled a woman could not be sentenced because the behaviour had no penalty under the act.

Other offences without a penalty include sexual assault, consensual sexual acts with children, sexual exploitation and grooming of children, and sexual offences against mentally disabled people.

Justice Minister Jeff Radebe said the government would also appeal the ruling.