More than half a million vehicle rentals throughout Europe could have their emissions offset in a voluntary carbon offsetting scheme unveiled by vehicle rental firm Europcar.

The firm is introducing a scheme this year that will allow customers to pay to offset the emissions from their rental.

The compay, which provides more than 10 million rentals a year, is expecting about 5% of customers to sign up for the voluntary scheme.

The proposals were announced at annual results of the firm, which revealed it has grown to a turnover of more than €2 billion following following acquisitions including Vanguard EMEA, owner of National and Alamo in the UK.

It is also investing in other environmental projects, including a car club service in an as yet unconfirmed major city.

Car clubs provide vehicle rental by the hour to members, with hi-tech equipment allowing customers to book vehicles as little as half an hour in advance.

Salvatore Catania, chief executive officer of Europcar Group, which has a total fleet of about 215,000 vehicles, said: “The CO2 scheme will be rolled out to all countries.

"It is not a marketing tool, it is part of a 10 year commitment we have shown to the environment. It is serious and delivers a real benefit.”