Ken's road charge doubles after 10pm

Thousands of motorists will find themselves paying £10 - not £5 - to drive in Ken Livingstone's congestion charging zone.

Under a little-publicised rule any driver too busy to pay the standard daily fee on time will find it doubled.

Drivers will have up until 10pm to pay the charge by telephone, internet, at a designated local shop, petrol filling station or vending machine. However, anyone who misses the deadline will have to pay the higher rate, sending more money cascading into Transport for London's coffers.

Today motoring organisations claimed almost no one knew about the £5 penalty clause which they described as unfair. But the Mayor's office insisted it had consulted widely on the payment.

"This is very harsh, but then the whole scheme is," said Rebecca Rees of the AA. "It is unfair that someone who travels into the zone and who then tries to pay, possibly at the end of a busy day, is in effect fined. They are not, after all, trying to evade but to pay. This is just about raising more money. It's about cashing in.

"How do we know they will be able to get through to the call centre? And what happens if they can't? This scheme will make drastic changes to people's lives but too many motorists are simply unaware of how it will work.

"So far the information has not been forthcoming, despite us asking for it. Around 75 per cent of our members say they will carry on driving and have to pay the charge. Congestion charging will become another tax."

Edmund King of the RAC Foundation, said: "It would have been far fairer if they could have put off the rise until at least the next day. Many motorists are simply not aware of this ruling and we hope Transport for London will publicise it properly.

"It is going to be another irritation for motorists. They will have to remember to have change for the parking meter and to get back in time to avoid a fine, while also keeping one eye on the petrol gauge and remembering to fill up.

"Now they will also have to keep reminding themselves to pay the charge. No doubt there will be dozens of motorists driving around with little bits of paper stuck to the dashboard, trying to remember."

Transport for London denied it had kept quiet about the extra £5 fee for late payers, which it prefers to call a surcharge.

It also denied it was a tax on people who won't be able to register before travelling into the centre of London, and who might find it difficult to pay up before 10pm.

A TfL spokesman said: "It doesn't take a genius to work out that we want people to pay early and this is supposed to be the incentive.

"We don't want everyone paying together late in the day and overloading the payment system.

"Originally, if people paid after 7pm on their day of travel they would have had to pay £10 but after consultation, we made it later."

However, the AA said that four out of five drivers in London were still in the dark about congestion charging. "We must have hard information, and quickly, as congestion charging could make a lot of changes to Londoners' lives and they don't know what to expect," said Ms Rees.

Anyone who forgets to pay before midnight on the day they cross the charging zone or drive within the boundary will get an £80 fine - which drops to £40 for prompt payment.

Congestion charging is intended to raise £130million a year, although Tory critics on the London Assembly claim the true figure will be nearer £80million.