The Human Rights and Democracy Movement in Tonga says a March planned for NEXT Thursday could be the biggest in local history.
The march is to protest against the high price of electricity provided by Shoreline Power Company, which is partly owned by the Crown Prince Tupouto'a.
Pro-democracy MP, Akilisi Pohiva, says the protest was originally scheduled for this weekend but was delayed so it could coincide with the opening of parliament.
He says he expects thousands of people to sign a petition and participate in the march.
"The exact concern is the very high cost of electricity, that is the purpose of the march. The petition requests that His Majesty to return electric power to government and of course there are other related issues involved in the petition."
Mr Pohiva says the movement is using television to promote the march.