The head of the Fiji Islands Council of Trade Unions says the new political party decree spells the end of all the country's political parties and has to be revoked.
The decree requires existing parties to register with 5,000 members from across the country by February the 12th.
They will also have to pay more than 3,000 US dollars to register.
Attar Singh says it will be difficult to operate a party, even if one was successfully re-registered.
"It is, mind you, a decree that has been made without any consultation with the political parties, yet there are other decrees that have been made in Fiji, in different times, where the people whose affairs it intended to regulate were consulted. Here, there's been no consultation, with any of the political parties on this. So it's a very, very serious matter and that is why I am saying that this is not something that we can follow, and it is a piece of legislation that needs to be revoked."
Attar Singh says a provision stopping union officials from being members of political party is a breach of both human and workers' rights.
The government has refused to comment on the decree to Radio New Zealand International.