Aiyaz Sayed-Khaiyum has resigned as the general secretary of the opposition FijiFirst party, which is also the largest in the current parliament.
In a letter, which was shared to FijiFirst's social media, Sayed-Khaiyum cites medical reasons for his departure.
"This resignation will ensure that the incoming acting general secretary or general secretary will be able to fulfil all the requirements and responsibilities expected of one holding such a position, including FijiFirst's compliance with all the relevant laws," he wrote.
Sayed-Kahiyum also attacked the current government of Fiji in the letter, saying it has taken political power to mean that it can undermine the principles of constitutionalism and override the supreme law of the land.
"These breaches are evident almost daily through pronouncements by politicians in government, various governmental decisions and policies," Sayed-Khaiyum wrote.
"Within a year we have seen that the current Fijian Government does not care about nor empathise with ordinary Fijians; with the gap between the rich and the poor increasing, increase in cost of living, reduction in social wages (such as free education and access to free GP services), reduction in the purchasing power of the Fijian dollar; and there is no rise in wages despite the imposition of increased VAT and other cost impact fiscal measures.
"Simultaneously because of lack of economic savvy and commercial and financial nous, new infrastructure development is almost non-existent.
"Such actions and inactions of the arms of the State and those who hold unbridled political power are antithetical and an anathema to a rules based and limitation of power system. As a result, we have seen large numbers of Fijians leave our shores."
RNZ Pacific has reached out to the Fiji government for comment.
It is not the first time Aiyaz Sayed-Khaiyum has attacked the current administration.
In June, he alleged Sitiveni Rabuka's government was offering people unfair advantage on the basis of "political allegiance" but defended Frank Bainimarama's previous FijiFirst government, saying it made appointments to government boards and institutions due to "their capability or the capacity to assist".
This criticism was downplayed by Rabuka.
While not categorically denying the accusations, Rabuka said the opinions of detractors did not worry him.
"[My reaction is] that I should not worry about that," Rabuka told RNZ Pacific.
"It is a good thing that people speak out [about good governance concerns]."
There were some Fijians who claimed Rabuka's coalition was walking the same path as the previous FijiFirst government, which was also accused of rewarding party supporters with government jobs and contracts when it was in power from 2014 to 2022.
Sayed-Khaiyum was granted permission to travel to Singapore for a medical review in September, despite facing a court charge of abuse of office for his time as acting prime minister.
The Suva Magistrates court has confirmed his next appearance is set down for 16th January for mention.
FBC News reported the party had informed the Acting Registrar of Political Parties, Ana Mataiciwa, that Faiyaz Koya has been appointed as Acting General Secretary of the party.