Clark, who is visiting Australia, told reporters that Green had been declared "persona non grata" by the government of self-appointed Prime Minister Commodore Frank Bainimarama, who seized power in a coup in December.
Green had "represented faithfully the position of the New Zealand government and I suspect that is the reason why he is being sent home," she said.
Australian Foreign Affairs Minister Alexander Downer said he was dismayed at the Fijian action.
"If the so-called interim government in Fiji thinks that the next best thing for it to do is to start expelling diplomatic representation from Fiji, I can only advise them that will be extremely counter-productive," Downer said.
2014: The Year in Music [PHOTOS]