Pro-democracy groups plan to march in the Tonga capital, Nuku'alofa, tomorrow and will again petition the King to make his government fully democratic.
The demonstrators will include public servants who staged a prolonged strike last year.
That action sparked calls for political reform, and petitions were presented to the King laying out the changes the people wanted.
But one of the People's Representatives, Akilisi Pohiva, says they have been ignored by the King, so will now try to force parliamentary debate on the issues.
"We will of course submit a private bill to Government, in the coming session, to discuss or to deliberate for the amendments to the constitution which we submitted to His Majesty on the 7th of December last year, to be made legal, part of the constitution."
Mr Pohiva says the marchers also want to raise their opposition to Tonga joining the World Trade Organisation and the government's plans to borrow tens of millions of dollars to fund the repurchase of the electricity supplier, Shoreline.
