Dominique de Villepin, the former French prime minister, illegally benefited from an early retirement scheme for diplomats under which he walked away with nearly 100,000 euros for a day's work, official sources have told The Telegraph.
The payment was made after Mr Villepin returned to the French foreign service for just one day after an absence of 20 years.
After the handsome pay-off was revealed by The Telegraph earlier this month, the French foreign minister insisted that it was in line with a mechanism set up for diplomats to retire early.
But official sources have now told this newspaper that following extensive press coverage of the affair in France, the state body that oversees civil servants’ pensions examined Mr Villepin’s case and concluded that it was not legal.
The pay-off infuriated many French as it came at a time when Socialist President François Hollande's government is preaching austerity, raising taxes and making savage cuts across the board.
Neither the foreign ministry nor Mr Villepin's spokesman responded when asked by The Telegraph if the politician, best known abroad for his impassioned speech to the United Nations in 2003 against the invasion of Iraq, was being asked to repay the money.
Mr Villepin, 60, was last September taken back into the diplomatic service - which he left in 1993 - for just one day, which the ministry said enabled him to to qualify for the pay-off.
But the Service des Retraites de l'Etat, the body overseeing pensions, says the early retirement mechanism was for diplomats who had served out their full career at the ministry, and therefore Mr Villepin did not qualify, sources said.
Mr Villepin served as foreign minister from 2002 to 2004. Ministry spokesmen insist that the current minister, Laurent Fabius, was not informed of the decision to take his predecessor back into the ministry nor of the pay-off he received.
But Jean-François Copé, the leader of the opposition UMP party and himself a former minister, said Mr Fabius must have known about it.
"Of course he was informed. It's compulsory," he told The Telegraph.
Mr Fabius is, like Mr Villepin, a graduate of the Ecole Nationale d'Administration (ENA), an exclusive university which produces many of the French elite. Mr Villepin was a classmate of President Hollande at ENA.
When initially contacted by the Telegraph two weeks ago, Mr Villepin's spokesman said he had been paid the bonus due to an "administrative error" which he had sought to "rectify".
The foreign ministry ignored repeated questions as to whether there had been a mistake regarding Mr Villepin, and then issued a statement saying it was entirely legal.
It sent The Telegraph a scan of an official decree dated 7 October 2013 that said Mr Villepin was benefiting from the retirement mechanism.
But this decree did not appear to have been published on the usual official website, which on that date published similar decrees naming three top executives in the foreign service who were benefiting from the same mechanism.
The ministry did not respond to queries as to whether the decree regarding Mr Villepin had actually been published or not, and if not, why not.
Read more of this report from The Telegraph.