With rising congestion, the Liberal Democrat transport spokesman Alistair Carmichael warns it would be irresponsible not to consider all possible remedies. But he argues road pricing should only be considered as a replacement for car tax, not an additional charge.

Reading the right-wing press over the past few months you would have been forgiven for thinking that the public is massively opposed to any new system of charging for road use. The myths spread by the Association of British Drivers, the people behind the petition on the 10 Downing Street website, have gone largely unchallenged. They are an organisation which denies that global warming is happening and argues that our carbon emissions have no impact on the environment. Despite weeks of scaremongering, when asked, two-thirds of people would support road pricing if the money raised was used either to cut other road taxes or to improve public transport.

The Liberal Democrats believe that climate change is the biggest challenge facing our world today. Currently transport is responsible for 27 per cent of the UK’s CO2 emissions, with road transport accounting for 95 per cent of those emissions. The government estimates that congestion on our roads is set to increase by a further 25 per cent by 2015. This follows a period over the last 25 years when road traffic has increased by over 80 per cent. According to the Eddington Report if current trends continue congestion will waste £22 billion worth of time in England alone by 2025.

Whatever you views on road user pricing, for the good of our environment and our economy, the status quo is not an option. It is irresponsible not to look at new ways to price road use to ensure that those who pollute the most pay the most and to avoid gridlock on our roads. The CBI, for example, has argued that road charging would result in huge benefits from reduced journey times and therefore better-planned deliveries.

The last Conservative government tried to build their way out of this problem. This simply did not work, resulting only in more cars using the widened and new roads. It would appear that they still support a massive road building programme, paid for by road pricing. Earlier this year the Conservative Party leader said, “We should also look at road charging. There isn’t an endless pot of money – so I think new roads may need be to paid for by tolls or some form of road pricing.”

The Liberal Democrats have consistently said that we will only support a national road pricing scheme if it is a different way of taxing motoring, not an additional way of raising revenue. Cuts in vehicle excise duty and fuel tax must offset the charges levied by any road pricing system. We also recognise that some road user pricing schemes could have civil liberties implications. So-called “passive technology” must be used so that no tracking is involved.

I am not in any way surprised that the online petition got the extent of support that it did. After 10 years of Gordon Brown as chancellor and Tony Blair as prime minister you have to expect that people will be cynical about any new form of taxation. Their record, after all, is not good. Gordon Brown has only ever seen “green taxes” as a way of increasing the take for the treasury. He has never committed to using them properly as a means encouraging changes in our behaviour to protect our environment.

It is clear that a national debate is under way on road user pricing. Mr Brown, as prime minister, will have to make his intentions clear or risk being on the losing side.