The head of the Paris regional transport network admitted on Monday that the city's metro system is near-impossible for disabled people to navigate as the French capital prepares to host the Paralympics.

The Games start on Wednesday, with a lack of accessible metro transport for disabled visitors a major gripe.

The first Paris metro opened in 1900 and the network has grown into the busiest system in the European Union, with more than 300 stations spread over 16 lines carrying over four million passengers daily.

But only 29 stops are wheelchair-accessible.

The city's historic metro lines "remain the weak spot" in terms of accessibility, said Valerie Pecresse, who as president of the Paris region also runs its transport network.

She called for a massive effort to fix the problem.

While all buses running in central Paris can take wheelchairs, only 25 percent of rail services – metros, trams and the RER suburban mass transit system – were accessible, she said.

Most of the metro could be modernised in terms of accessibility, she told reporters, although it would take 20 years and cost between 15 and 20 billion euros (US$16.7 to 22.3 billion) in investment.

Such an effort "could become the great project of this decade", she said, dubbing the idea "A Metro for All."

Paris's preparations for the Paralympics, which run to September 8, has highlighted the lack of accessible transportation in the French capital.

However, Pecresse said some solutions had been put in place for the Games, including around 100 minibuses to take disabled visitors to competition venues.

There would also be a smartphone app to help them prepare their journeys.

Authorities expect up to 300,000 daily visitors during the Paralympics, about half that of the Olympics. (AFP)