The aim is to make it possible for local authorities to allow zero-emission vehicles to benefit from incentives such as cheaper parking.

The government hopes it will boost electric car sales, helping it achieve its 2050 target of net zero emissions.

But Friends of the Earth said without better financial incentives and more charging points, little would change.

The government is asking industry and the public for their views on how to implement the scheme.

"As the UK moves at pace towards net zero emissions, the initiative aims to raise awareness of the increasing number of zero tailpipe emission vehicles on UK roads," said the Department for Transport (DfT).

"Through the introduction of green number plates, local authorities would have a useful visual identifier should they wish to introduce incentives to promote the use of zero-emission vehicles, such as allowing these drivers to use bus lanes and to pay less for parking."

CPT UK, the trade body for the bus and coach industry, said it would be a mistake to allow electric cars to use bus lanes.

"If local authorities allow some cars to use bus infrastructure, which is already severely strained and in need of significant investment, we will simply increase congestion for bus passengers and drive people off the bus and back into cars the vast majority of which are not electric," said chief executive Graham Vidler.

Sales of all-electric vehicles (EVs) are up sharply since last year, leading to suggestions the market has reached a turning point.

But all-electric vehicles still represent only a fraction of total car sales and there are challenges to uptake, including a lack of charging points on roads and too few low-cost models.

The government said a similar licence plate scheme introduced on a trial basis in the Canadian province of Ontario had led to an increase in electric vehicle registrations.

However, RAC head of roads policy Nicholas Lyes said: "While the sentiment seems right, there are question marks as to whether drivers would see this as a badge of honour or alternatively it could foster resentment among existing drivers of petrol and diesel vehicles.

"On the face of it, drivers we've questioned don't seem too impressed - only a fifth think it's a good idea and the majority said the number plates wouldn't have the effect of making them any more likely to switch to an electric vehicle."

Friends of the Earth campaigner Jenny Bates urged the introduction of a national scrappage scheme, saying it would "help fund a switch to a cleaner vehicle or greener transport alternative".

'A real incentive'

Rod McClair-Burgess regularly drives his electric car into the City. He says, incentives such as being allowed to use bus lanes would make his journey "faster and easier" and be "a huge plus".

"That would probably half my commute time and would be a real incentive for me for driving a car like this," he says.

'Positive and exciting'

Transport Secretary Grant Shapps said the UK was "in the driving seat" of global efforts to tackle vehicle emissions, but wanted to "accelerate" progress.

"Green number plates are a really positive and exciting way to help everyone recognise the increasing number of electric vehicles on our roads," he added.

The DfT has issued three potential number plate designs and is consulting on which one should be adopted.

The move comes as part of the government's £1.5bn Road to Zero Strategy, a package of measures aimed at making the UK "the best place in the world to own an electric vehicle".

The Norwegian capital Oslo has plenty of electric vehicles. You can spot them relatively easily by looking for an "e" at the start of each number plate.

E-vehicles park for free in some public car parks which are loaded with charging points.

And a commute in or out of the city in an electrical vehicle is generally much faster than in a petrol or a diesel car because on several main roads, electric cars can zoom down the bus lane.

This type of incentive does exist in some parts of the UK (for example Nottingham has a bus lane which e-vehicles are allowed in) but the government hopes by marking low emission vehicles out with a green number plate more councils will do more to persuade drivers thinking about making the switch.

In Norway, such incentives have played a role.

But high taxes for petrol and diesel cars as well as tax breaks for electric cars, together with a good network of fast-charging points, have also been critical factors in pushing Norway beyond the electric adoption tipping point.

In the UK, consumers get £3,500 towards the cost of a new electric car and if the vehicle is valued at under £40,000 it is exempt from annual vehicle tax.

But the government admits the UK's charging infrastructure still needs to improve.