Fiji's National Federation Party has called for the immediate resignation of the minister in charge of the elections, Aiyaz Sayed-Khaiyum.
He is also the attorney general and the holder of several other portfolios.
The NFP says by becoming an office holder in the regime's proposed party, Mr Sayed-Khaiyum has compromised his position as minister.
It says the Political Parties Decree bans trade unionists from the elections by classifying them as public officers although they are funded privately through union members.
The party says while Mr Sayed-Khaiyum preaches the rest of the country to walk the moral high ground, he violates these principles with impunity.
It says the September elections will lose all semblance of being free, fair and credible, if Mr Sayed-Khaiyum continues to hold both the position of minister and general secretary of the proposed political party.
The NFP call comes a day after the Labour Party called for his resignation.