TOKYO - A JAPANESE legal review panel has labelled as 'unjust' a prosecutors' decision not to indict a supporter of the trade minister over a political donations scandal, officials said on Wednesday.

Similar charges in the scandal have badly damaged the main opposition party in recent months, leading to allegations in a crucial election year that the investigation by Tokyo prosecutors was politically motivated. The citizens review panel found that 'from what we have learnt from the record, we cannot say the investigation was done thoroughly,' referring to a probe of an aide to Trade Minister Toshihiro Nikai.

'An extensive investigation... is expected' into the case of Shinya Izumi, an upper house member who was in charge of accounting at a group supporting Nikai's party faction, the panel said according to Jiji Press.

Under Japan's legal system, panels of 11 citizens each are randomly chosen for six-month periods nationwide to review key decisions by local prosecutors on whether or not to indict suspects in criminal cases. Prosecutors must review cases that are challenged by the panels, which are called the Committees for the Inquest of Prosecutions.

The donations scandal, which rocked Japanese politics this year, centred on a construction company that, prosecutors told media, was suspected of having given illegal donations to politicians through front groups. Tokyo prosecutors, who focus on serious white-colour crime and enjoy a large degree of autonomy, in March indicted an aide to Ichiro Ozawa, the former leader of the main opposition Democratic Party of Japan.

Mr Ozawa, long seen as the frontrunner against conservative Prime Minister Taro Aso in elections that must be held by October, stepped down over the scandal several weeks later, alleging political interference.

Tokyo prosecutors, who often pass on investigation details to Japanese media, had told journalists they were investigating supporters of Nikai and other ruling party figures but never indicted any of them. The case puzzled many observers after both opposition and ruling party figures, including a former prime minister, had admitted to having received money through front groups of the company, Nishimatsu Construction.

The top government spokesman, Chief Cabinet Secretary Takeo Kawamura, told reporters on Wednesday: 'I hope that prosecutors deal with the case appropriately after the committee ruling.'

The deputy chief prosecutor of the Tokyo Prosecutors' Office, Tsuneta Tanigawa, said in a statement: 'We will deal with the case after carefully examining the content of the ruling.'

Mr Aso's Liberal Democratic Party has ruled Japan for almost all of the past half century. -- AFP