The hearing relates to a disputed government compensation payment to businessman Bernard Tapie in 2008 when Orange CEO Stephane Richard was working for Christine Lagarde, then France's finance minister.

Lagarde, who now heads the International Monetary Fund, faces a trial on charges of negligence concerning a decision to make a settlement payment of some 400 million euros (300.07 million pound) - money an appeals court recently ordered Tapie to pay back to the state.

Richard, who denies any wrongdoing, is already under formal judicial investigation over the matter and could ultimately be sent to trial too.

Wednesday's news that he will also have to appear before an administrative court on Jan. 21 comes at a bad moment, as he is currently involved in high-stakes talks for state-controlled former monopoly Orange to buy Bouygues Telecom, a rival telecoms business controlled by tycoon Martin Bouygues.

Richard is one of three people being sent before the Cour de discipline budgétaire et financière (CDBF), an administrative tribunal that oversees public budgetary discipline, on a charge of "violating rules to protect public money and ... poor management resulting in irregularities".

The CDBF is not a mainstream French court and only has power to impose a fine but there can be no appeal against its findings unless there is new evidence.

On the separate judicial front, Richard was put under formal investigation last year in connection with the now-scotched settlement payment to Tapie. Under French law, such a step often, but not automatically, leads to trial.

Lagarde's trial date has yet to be set, but it will be heard by the Cour de Justice de la Republique, which judges ministers for offences in office. She has said there is no basis for any charge against her.

The Tapie affair dates back to 1993 when he sold his stake in sports company Adidas to the now-defunct state-controlled bank Credit Lyonnais, after being named a minister in the Socialist government of then President Francois Mitterrand.

Tapie later claimed the bank defrauded him after it later resold his stake for a much higher sum. He started what turned out to be one of the longest legal battles in recent French history.

(Reporting by Mark Potter)