At least one in ten vehicles on Scotland's roads must be electric by 2020 to meet Scotland's climate change targets, an environmental charity report said.

The WWF Scotland study said that electric vehicles (EVs) have an important role to play in helping to achieve the Scottish Government's 2020 target of reducing greenhouse gas emissions by at least 42%.

It said that by then at least 290,000 petrol-driven cars will have to be replaced with EVs, while the projected increase in car use must also be reversed.

If the expected increase in car use is not tackled the total number of EVs required to meet the 2020 target shoots up to over 1.5million by the same date, according to the report.

The environmental group called on the Scottish Government to set out a plan to roll out electric vehicles across the country in its forthcoming Low Carbon Vehicle Action Plan.

Dr Sam Gardner, climate change policy officer at WWF Scotland, said: "If the transport sector is to play its full part in helping to meet our climate change targets there needs to be a real surge in the number of electric vehicles on Scotland's roads.

"To help kick start this transformation the Scottish Government must set out a plan to support the roll out of electric vehicles in Scotland and as a first step commit to ensuring that the public sector fleet is 100% electric by 2020.

"Government leadership is essential to drive the market and make the electric vehicle a common feature of our roads.

"In these times of tight public spending government action is required to realise the jobs potential of this new industry."

He said that EVs are not a "silver bullet" in response to climate change, and said their introduction must be matched with a far greater effort to reverse current reliance on private vehicles.

The report, titled 'Watt Car?: the role of electric vehicles in Scotland's low carbon future', said that for EVs to make the greatest impact towards the 2020 targets they must be seen as part of an overall package to stabilise road traffic levels and decarbonise the power sector by 2030.

Emissions from an EV powered from the current UK grid are approximately 50% lower than from the average internal combustion engine car.

The report said that increased electricity demand resulting from a new fleet of EVs is relatively modest, but that in order to minimise the need for additional electricity generation and ensure EVs support the growth in renewables, the new demand must be fully integrated into a smart energy system.

Pilot programmes with EVs have been taking place across the UK.

In Scotland Glasgow City Council has joined forces with partners including ScottishPower, Allied Vehicles and Axeon Batteries to trial 40 EVs and supporting infrastructure in 2010.

Gordon McGregor, Energy and Environment Director at ScottishPower, said: "The growth of electric vehicles will play a key role in the overall reduction of CO2 emissions in the UK and across the world, alongside the on-going decarbonisation of electricity generation.

"As CO2 emissions are increasingly reduced from the process of generating electricity, the environmental benefits of electric vehicles will only ever increase."