Tonga's Prince Tu'ipelehake, a nephew of King Taufa'ahau Tupou the 4th, has confirmed he will oppose constitutional changes which are being debated in the Assembly this week.
Opponents of the legislation say it will place severe curbs on media freedom.
Organisations such as the pro-democracy movement say it will be stopped if they can win the support of several members of the nobility.
Prince Tu'ipelehake says the measure infringes on media freedoms, but he is not sure how the rest of the Assembly will vote.
"I can't really predict, I think the general feeling is against it."
Prince Tu'ipelehake, who chairs the Legislative Assembly, says the changes would bring the country into disrepute.
Earlier this month, the Government removed one of the contentious changes from the planned amendment - dropping a provision which would have stopped any judicial review of Government rulings.