A FRENCH investigation into a Las Vegas tech party is putting new pressure on President Emmanuel Macron's labour minister - and possibly the president himself - as they pursue difficult reforms to French work rules.

The Paris prosecutor's office has opened a formal judicial inquiry into suspected irregularities in the organisation of a costly, high-profile event at the 2016 Consumer Electronics Show that Mr Macron headlined when he was a government minister.

The inquiry is for "favouritism", but it does not name a suspected perpetrator, leaving it to investigators to determine who might be at fault.

The company tasked with organising the "French Tech Night" event - advertising firm Havas - is believed to have won the contract without undergoing open tender procedures, among other suspected problems.

It is unclear whether Mr Macron was aware and the investigation does not target him directly. It is problematic, however, for his labour minister, Muriel Penicaud.

She was working for an agency under the economy ministry - then headed by Mr Macron - that reportedly signed off on the Havas contract.

Ms Penicaud has acknowledged a "procedural error" in the process but says she then launched an internal and external audit and addressed the issue.

Mr Macron used the trip to promote French technology start-ups, a pillar of his strategy for boosting the French economy.

Another pillar is the labour law Ms Penicaud is spearheading this summer, which would make it easier to hire and fire workers and reduce the power of unions.