The company now expects free cash flow of at least 4.5 billion euros ($4.74 billion) for 2023, against a previous estimate of between 4 billion and 4.5 billion euros.

Vinci's order book reached 63.3 billion euros at Sept. 30, a record high level according to the company. The group's net financial debt stood at 18.6 billion euros at the end of the nine-month period, down from 20.1 billion euros a year ago.

The French 2024 budget, currently being discussed in parliament, includes a tax on the transport sector which would apply to both the Vinci-owned Lyon-Saint-Exupéry Airport and the group's subsidiaries operating French motorways via state concessions.

"We intend to use all the available avenues to appeal," Chief Financial Officer Christian Labeyrie said in a call with analysts, adding "higher taxes unavoidably mean higher tolls."

The group said last month the tax would represent a 260 million euros surcharge based on its 2022 figures.

($1 = 0.9498 euros)

(Reporting by Victor Goury-Laffont; Editing by Chris Reese)