Fiji's opposition National Federation Party says a government bill currently before the house would suppress the freedom of speech if enacted.
Submissions are open on the Parliamentary Powers and Privileges Bill, which imposes penalties on any person who defames, demeans or undermines the sanctity of parliament.
The party's leader, Professor Biman Prasad, said clause 24 of the bill threatened people's right to criticise their representatives.
"In a democracy, it's the people who elect their representatives to parliament and it is therefore the right of the people to make a decision of the performances of their representatives. If they feel they need to have an opinion about them and their performance then they ought to have the right to do so without any restriction or without any threat of fines or jail terms."
Clause 24 of the bill proposes fines of about $US15,000 and imprisonment of up to five years.
Corporations convicted of contravening the clause risk a fine of about $US50,000 with each director and manager liable for prison terms of up to five years.
The committee considering the bill is hearing oral submissions while written submissions will be accepted until 15 May.