A controversial project by the Socialist mayor of Paris to pedestrianize a section of the River Seine's Left Bank came into force on Monday when part of a highway was permanently closed to cars.

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From now on cars will no longer be able to travel along the 2.5km of road between the Musée d’Orsay and the Pont de L’Alma (Alma Bridge) on the city's famous Rive Gauche

The tarmac will be replaced by around 4.5 hectares of green space, including 1800 square metre floating gardens, which is due to open for use in spring at a reported cost of €35 million.

The city’s mayor Bertrand Delanoë said the changes to the Left Bank, designated an UNESCO  World Heritage site in 1992, are for the benefit of residents and tourists.

“It is one of the most beautiful places in the world,” the mayor told radio station France Info. “The bank of the Seine between the Musée d’Orsay and the Pont d’Alma is an urban motorway, it is an aberration.

“We are returning this part of Paris to Parisians and lovers of Paris,” he added.

But motorist groups have vociferously opposed the scheme claiming it will extend journey times and lead to traffic bedlam at rush hour.

Pierre Chasseray, from the organization '40 million motorists' told Le Parisien that the closure will simply clog up the capital's other main arteries.

"Cars are not going to disappear with a wave of a magic wand," Chasseray said.

Delanoë's project had been blocked by the previous conservative UMP government but was eventually given the green light last year after the Socialists took power.

Since he became mayor in 2001 Delanoë has had his sights firmly set on trying to unclog the French capital’s streets from the gridlock it faces on a daily basis.

His city-wide bike-sharing scheme - Vélib', was introduced in July 2007 and is considered a great success. December 2011 marked the introduction of the much-heralded car sharing initiative Autolib, in which users can pick up and drop off electric ‘Blue cars’ at dozens of docking stations around the city and beyond.

Delanoë was also credited for introducing the annual 'Paris Plages' (Paris Beach) when a section of the Right Bank is transformed from a highway into a beach for part of the summer.

The mayor has also recently moved to ban classic cars from the city centre in a bid to reduce pollution.

Like these other projects Delanoë accepts his latest scheme may experience a few hiccups at first.

“It will take a few weeks or a few months to adapt to, like all the changes I have made since 2001,” Delanoë told BFMTV.