French Polynesia's opposition Tahoeraa Huiraatira Party says the purchase of an atoll now at the centre of a police investigation was approved by all relevant authorities.
The Tahoeraa leader and former president, Gaston Flosse, says his government acquired Anuanuraro atoll from a leading pearl producer, Robert Wan, three years ago to save it from being bought by foreigners.
The party says Japanese investors offered nearly 11 million US dollars but the government got it for 9 million which is five times its reported value and the basis of the investigation.
Mr Flosse's deputy and son-in-law, Edouard Fritch, as well as Mr Wan are among those under investigation for alleged misuse of public funds.
Mr Flosse refused to be questioned by the police investigator sent from France, prompting the Tahoeraa to boycott the assembly last week in protest at the probe.
He also said the probe ignored the role of the former finance minister, Georges Puchon, who approved the transaction.
Mr Puchon, who was expelled from the Tahoeraa for questioning Mr Flosse's stance following last February's election defeat, has rejected personal responsibility for a presidential decision.
And he says he has not seen the reported offer from Japan to buy the atoll in the Tuamotu archipelago.
Mr Flosse's lawyer says there is no case to answer as paying a substantial sum for an atoll cannot amount to a breach of the law.