Motorists travelling across the two Severn crossings might be able to use credit or debit cards to pay toll charges from next year.

But the system could cost the Government up to £1 million a year to run because of the bank charges on the thousands of card transactions made each day.

Under the current system, motorists who do not have cash to pay the toll – £5.40 for cars – are allowed through but are ordered to pay the charge, plus a fine, within seven days.

The Highways Agency plans to get the law governing the two crossings changed to allow the introduction of a system where motorists simply swipe their credit or debit card through a machine to open the barrier.

Highways Agency project sponsor for the Severn crossings Chris Pope said delays in introducing the card-payment system had been caused by discussions over who would cover the cost of card transactions – but there would be no extra charge to motorists.

Severn River Crossing general manager Jim Clune said he expected cards to be accepted in the second half of next year.

Northavon MP Steve Webb said welcomed news and said: "We've been waiting for this for years. The crossings look like they've finally arrived in the 21st century."