A Tongan pro-democracy campaigner, Akilisi Pohiva, says they are not inciting violence by planning to hold a demonstration at the Pacific Islands Forum summit in October.
He says a letter that a coalition of pro-democracy groups sent to the Forum secretary-general, Greg Urwin, outlined why they wanted to draw attention to the lack of progress over political reform in the country.
Mr Pohiva says people still want the government to agree to hold a referendum on whether the public should elect all the MPs and allow the MPs to elect the prime minister who would then appoint all the ministers.
He says a proposal to change the constitution was first introduced in 1975 but there has been far too little progress since.
"I think we have done enough to persuade government to do the right thing and in my opinion we have covered all the peaceful avenues in our struggle to get things done and yet nothing happened, so it's up to the people to make a decision at this point of time."
Mr Pohiva says the government committee set up last year to look at political reform in the kingdom is moving too slowly.