Fiji's former interim defence and immigration minister, Ratu Epeli Ganilau, says he resigned on Tuesday because of disagreement over how to deal with an employee of a US company, Fiji Water.
Ratu Epeli has told the Fijilive website the reason he quit relates to the Fiji Water director of external affairs, David Roth, but he declined to elaborate.
Reports say he objected to plans to have him deported.
Fiji Water is a key export business in Fiji but it has been in dispute with the interim regime over tax and royalty issues.
A spokesperson for Fiji Water at its California headquarters says a statement on the affair will be issued tomorrow.
The interim minister in charge of industry and investment, Aiyaz Sayed-Khaiyum, has declined comment as has the new acting interim prime minister, Joketani Cokanasiga.
A former land force commander says Ratu Epeli's resignation is a signal of instability within the interim regime.
Jone Baledrokadroka, who is now an academic in Canberra, says the timing of the resignation while Commodore Frank Bainimarama is in China is ominous.
"It is quite disconcerting I suppose for the people of Fiji when you have an illegal prime minister out of the country and the acting prime minister was told to act on his behalf jumped ship. So, I mean it doesn't show stability as far as the regime is concerned and it leaves the country without a leader and at the moment you have a acting, acting prime minister, which is Joketani Cokanasiga."