French President Emmanuel Macron's chief of staff Alexis Kohler ha been placed under investigation over links to an Italian shipping giant, anti-corruption prosecutors said Monday.
The probe will look into Mr Kohler's career as a senior civil servant in the economy ministry, where he served as cabinet director to Mr Macron during his time as minister from 2014-2016.
The financial crimes prosecutor office said it would check whether Mr Kohler respected conflict of interest rules for civil servants as he "could have dealt with issues of interest" to the Mediterranean Shipping Company (MSC).
Mr Kohler's mother is a cousin of billionaire Rafaela Aponte, who founded MSC with her husband Gianlugi in 1970. The group is now a global leader in container shipping and cruise holidays.
Mr Macron's office dismissed the allegations of wrongdoing, first revealed by investigative website Mediapart, as "completely unfounded".
"Alexis Kohler will willingly send to prosecutors all of the documents that prove his respect of the law during his professional life," the presidency said.
The case is an unwelcome development for Mr Macron, 40, who has been labelled the "president of the rich" by leftist opponents accusing him of being too close to company owners and entrepreneurs.
It also adds to a list of legal investigations targeting political allies which have the potential to cause problems if any of the allegations are proven in court.
Labour Minister Muriel Penicaud, who also worked with Mr Macron while he was economy minister, is being investigated over an evening she organised in Las Vegas to promote French technology companies in 2016.
The contract to organise the event, which initially cost nearly €400,000 (Dh1.7 million) and featured Mr Macron as guest of honour, was not put out to tender, leading to accusations of favouritism.
She also denies wrongdoing.
Soon after his election last May, Mr Macron's close ally Richard Ferrand stepped down from his job as minister for social cohesion after being investigated over a property deal involving a public heath fund he headed.
And several other ministers from the centrist MoDem party, which backed Mr Macron as president, also withdrew from the government over an investigation into alleged misuse of EU funds for political parties.
The media-shy Mr Kohler, 45, is known for his close personal relationship with the president and was once described as "the last person Macron talks to at night and the first one in the morning" by an aide who knows both men.
He left the economy ministry in 2016 to join Swiss-based MSC as finance director but continued to work on Mr Macron's bid for the presidency in his spare time, providing advice on policy and strategy.
A graduate of Sciences Po university and the elite ENA school for civil servants, like Mr Macron, Mr Kohler was rewarded with the chief of staff position after Mr Macron's election.
His links to the Aponte family were not publicly known until they were revealed by Mediapart, whose reports formed the basis of a legal complaint by transparency campaign group Anticor last Friday.
The allegations against Mr Kohler relate to his time in the economy ministry when he was involved in decisions affecting a major French shipyard in the western city of Saint-Nazaire.
MSC is one of the most important clients of the strategically important industrial site, which was part-owned by Korean company STX until 2017 when it sold its shares to Italian group Fincantieri.
Le Monde newspaper reported that Mr Kohler sat on the board of STX France as a representative of the state from 2010-2012 and later dealt with the company while serving as a deputy cabinet director and then cabinet director from 2012-2016.
He always declared his family links and recused himself from decisions directly linked to MSC and STX, the presidential palace said in a statement to the newspaper.
In 2014, Mr Kohler attempted to leave the ministry for MSC but was prevented from doing so by an ethics watchdog.
He finally joined the company in 2016 as Mr Macron was launching his bid for the presidency.