France's Socialist government allowed conservative ex-prime minster Dominique de Villepin, 60, to return for one day's work in order to qualify for a €100,000 retirement windfall, Britain's Daily Telegraph reported on Tuesday.

Sources at the French foreign ministry told the paper that the charismatic former diplomat, who served as prime minister from 2005 until 2007 under the leadership of Jaques Chirac, returned to the diplomatic service – which he left in 2004 – in September for a day in order to receive the pay-off, equivalent to $138,500.

The British paper said it was unclear exactly what entitled Villepin to the payment and that "the exact details are shrouded in a French bureaucratic device called the 'career termination mechanism'."

The sources added that the move was likely approved by Foreign Minister Laurent Fabius and was not illegal. The ministry has so far not answered any questions about the pay-out.

According to the Daily Telegraph, officials are angry at the pay-off, which comes amid President Francois Hollande's unpopular austerity drive.

A spokesman for Villepin told the paper there had been an "administrative error which Mr Villepin has already asked to be rectified by the relevant authorities as soon as it was noticed", but did not explain what that error was, or whether the money had been returned.

A ministry spokesman added there had been "no discretionary or preferential treatment" for Villepin, who joined the diplomatic service after graduating from the elite French university ENA, where he studied with the President François Hollande.

Since his time as prime minister Villepin, who is most famous outside France for his 2003 speech at the UN against the Iraq war, has been on the fringes of mainstream politics.

He was an ardent critic of Nicolas Sarkozy and ran for president in the 2012 race as an alternative right wing option, before being forced to withdraw due to a lack of support.

Since then Villepin has headed his own international consulting firm, which pulled in a cool €1,676,900 last year, the Telegraph said.

French magazine L’Express valued his personal wealth at €4 million in 2012.