The Fiji Citizens Freedom Movement has demanded that the President's Office apologise for its actions in connection with the May 2000 coup.
The Movement says the office acted outside the constitution when the elected government was dissolved and Ratu Tevita Momoedonu was made prime minister.
It claims it was also unconstitutional to choose Ratu Josefa Iloilo as president and Ratu Jope Seniloli as vice-president.
The head of the Movement, James Bachu, says he will take the office to court if there is no apology within a month for ignoring the constitution.
"It was systematically put aside and I blame the presidents office for that. They had no reason to work outside the constitution because the constitution was never abrogated. The President had no legal right to dissolve parliament he abused his official capacity as president."
Mr Bachu's action is also directed at Ratu Sir Kamisese Mara who left the presidency during the coup.
Mr Bachu also says he is yet to name the people who masterminded the coup.