The number of UK motorists failing to pay vehicle excise duty (VED), also known as car tax or road tax, has more than doubled since the end of the paper tax disc.

An estimated 560,000 vehicles on UK roads are evading tax, according to official figures from the Department for Transport (DfT).

The RAC said it was a worrying increase on the previous figure of 210,000, recorded in 2013 before the paper disc became obsolete.

The latest data shows 1.4% of vehicles in use are unlicensed, which could cost about £80m in potential lost revenue each year, although some of this will have been recovered through enforcement activity or payment by arrears. The 2013 figure was 0.6%, costing £35m.

When the paper disc was ended in October last year the government said it would eventually save the Driver and Vehicle Licensing Agency (DVLA) around £7m a year. Motoring groups expressed reservations that it could lead to more motorists failing to pay duty.

RAC chief engineer David Bizley said: 'These are very worrying and disappointing statistics indeed.

'Sadly, the concerns we raised about the number of car tax evaders going up at the time the tax disc was confined to history have become a reality.'

He warned that the UK cannot afford the growth in lost revenue to continue 'for the sake of both road safety and the country's finances'.

DVLA chief executive Oliver Morley said: 'Almost 99% of all vehicles on the road are correctly taxed – that's around £6bn in vehicle tax passed to the Treasury every year.

'We write to every registered vehicle keeper in the UK to remind them when their tax is due and we have introduced a range of measures to make vehicle tax easy to pay. At the same time we are taking action against those who are determined to break the law.'

The DVLA said 75% of motorists pay tax online or over the phone, including 11 million who have switched to direct debit.

Motorists who have not paid tax can be spotted on automatic number plate recognition cameras or police checking VED data information.