Fiji's political parties have only 25 days to sign up 5000 members from across the country, and pay more than 3000 US dollars to register with the interim regime.
The decree came into force 28 days after it was gazetted on Tuesday, but it was two days before it was released to the public.
Existing parties which do not comply by the terms of the decree face fines or imprisonment for office holders.
The decree sets out public officers who may not be members of political parties, including public servants and trade union officials, but excludes the President, Prime Minister and Ministers and members of parliament.
Registered office holders in parties will also have to provide financial information on themselves, their spouses and their children.
The decree states that where a political party commits an offence, every office holder of that political party shall also be deemed to have committed the offence, and be liable for fines or imprisonment in some cases.
Anyone who resigns from a political party will have to do so in writing to both the party, and to the registrar.
The government has not responded to several requests to speak to Radio New Zealand International.