Mumbai: Switzerland has given the highest green rating to Toyota Motor Co''s hybrid car `Prius''.

In a draft study evaluating the environmental impact, including carbon dioxide (C02) emissions which contribute to global warming, of driving around 6,000 different cars, the Swiss government named Toyota''s Prius the world''s greenest car.

The list could also be used to impose an emissions-related tax on cars. The Swiss government said it hopes that the list - which is still in draft form and could be revised before it is finalised next year - will persuade drivers to buy cars which have the lowest impact on the environment.

Toyota, which is on its way to becoming the world''s biggest car maker beating General Motors, launched the Prius - a hybrid car which uses battery power and a combustion engine - in 1997 by Toyota.

It is the best-selling hybrid car on the road, although hybrids account for only a fraction of global car sales.

For Switzerland , renowned for its clean Alpine air and pristine ski slopes, the goal is to modernise the current fleet of cars and to make use of natural resources as efficient as possible, so that using cars will exert less pressure on the environment.

The draft list of top 20 cars published by Swiss newspaper NZZ am Sonntag had Fiat''s Punto 1.2 Bipower and its Panda 1.2 Bipower, the Daihatsu Cuore and Citroen''s C3 1.4i GNV among the top 5.

The draft will be sent to the industry for comments before being finalised.

Ford''s Transit and Transit 4x4, the VW T5 and Peugeot''s Boxer were in the bottom 5 while Nissan saw its Patrol GR 3.0 get the lowest rating.

The US accounts for more than half of Toyota''s Prius sales. The United States and China are the world''s top emitters of carbon dioxide, the main greenhouse gas causing global warming.