Five years ago Metro officials ordered extensive research to develop an antidote to the foul odours that have plagued the subway system.

Now they have produced Madeleine, named after one of the network's whiffyest stations.

The manufacturers say Madeline is composed of lemon, orange and lavender, with an extra hint of floral bouquet and underlying woody notes, accompanied by vanilla and musk.

But some, who have smelled the mixture, say it is more like disinfectant.

Either way it is said to be better than the foul odour caused by a combination of trains, five million daily passengers, homeless people using stations as lavatories and an inadequate ventilation system.

'Sweet, not violent'

Metro director Jacques Rapoport said: "We had to find a smell that was sweet rather than violent, that lingered for two weeks and that suggested a feeling of cleanliness and well-being rather than of filthiness being covered up."

Every month, 1.5 tonnes of Madeleine will be added to the system's cleaning products to overpower the existing smells of decaying bacteria, human sweat, urine, vomit, burning rubber and other unpleasantness.

Invalides station will be the first to benefit from Madeleine. Eventually it will be introduced across the 98-year-old network's 380 stations.

Field trials

It is not the first time the authorities have tried to freshen up the underground.

Madeleine's predecessor, Francine, a scent of lavender, eucalyptus and mint, was tested in 1993 and 1994. It was abandoned after generating more complaints than praise.

This time no chances were taken. Four scents, from an initial 500, were shortlisted for trials involving 5,000 Metro users.