The payment company has released new data showing that 7,424 penalty charge notices (PCNs) were paid by drivers using the Dartford Crossing, who were unaware that they could have just paid the road user charge of £2.50 per car, instead of the fine, if they settled within two weeks.

As a result, over £259,840 has been paid in fines at the discounted rate of £35 per PCN – but Dartsave added that with some paying the full £70 fine, the actual sum of overcharges paid could be double.

"This is another example of Dart Charge profiting from Dartford Crossing users being confused about their system and how it works," said Dartsave director Chris Billing. "It's another in a long line of issues we've encountered with Dart Charge.

“Questions should be raised about them issuing 601,256 PCNs in the first five months of going live as that's a huge amount. If the system worked perfectly, it would be more understandable but in our opinion it is deeply flawed."

"We've launched a petition at www.dartrage.co.uk to call for the Government to demand a refund from Sanef Operations Ltd, who will be paid £367 million to run the Dart Charge system over a ten year period," explains Billing.

"We believe the systemic issues mean it will never operate properly and should therefore be scrapped and replaced as soon as possible."

"Road users who have paid a penalty charge during their discretionary period can contact us for a refund of the difference," Highways England told Dartsave.