Participants in forums broadcast via unlicensed radio channels commit a criminal offence, the Office of the Telecommunications Authority says.

It issued the warning today after learning some Legislative Council by-election candidates plan to speak on illicit broadcasts next month.

Under the Telecommunications Ordinance, participation in unlicensed radio transmissions warrants a $50,000 fine.

It said illegal broadcasting interferes with other legitimate service providers and users, and warned it will enforce the law to ensure proper radio spectrum management.