The 38.5 billion euro (RM186 billion) Grand Paris Express development, one of Europe’s biggest infrastructure projects, involves building 200 kilometres (124 miles) of track and 68 stations and will be key to linking transport hubs and Olympic sites.

But surging cost projections may force President Emmanuel Macron’s government to delay the construction of some lines – an announcement on which is expected by mid-February – to avoid creating too big a hole in the public finances and breaking European Union budget rules.

“The delays and financing difficulties could harm the smooth running of the 2024 Olympic and Paralympic Games,” a cross-committee grouping of senators said in a statement.

The Grand Paris Express project includes an express line linking the capital’s main international airport with the city centre, metro lines serving deprived suburbs, and another linked to a technological research centre.

It was central to Paris’ boast of “easy-to-access rapid public transport options to 100% of Games venues” in Paris’ 2024 bid for the Olympics.

The new lines are also central to Paris’ efforts to improve public transport accessibility for handicapped users. Only 3% of the city’s metro stations are fully accessible to individuals with reduced mobility.

The senators’ worries add to those expressed by the Cour des Comptes, France’s independent audit body, which on January 16 estimated the projects’ overall cost at 38.5 billion euros (RM186 billion), more than 12 billion euros (RM58 billion) higher than the last estimate in 2013.

The audit body too said it had “serious doubts” about the project’s ability to open in time for the 2024 Olympics.

“We have six and a half years until the games. This may seem a comfortable gap but in reality, it is very short given the slow pace and complexities of our urban procedures,” said senator Philippe Bas.