Drivers have branded a traffic regulation as "bizarre" and "nonsense" after being hit with fines for advertising the sale of their cars.

In four separate cases in recent months residents say they were completely unaware of doing anything illegal and have vowed to challenge their fines.

The regulation, introduced by Barnet Council to clamp down on traders who advertise their wares on the borough's streets without a licence, is being used by parking wardens against motorists with for sale' signs in their car windows.

Nicki Hanison, 34, of Brooklands Road, Hampstead Garden Suburb, was fined in Temple Fortune after parking her car in a pay-and-display bay.

Her husband Paul, 35, said: "When my wife saw it she couldn't believe it. Apparently it's been advertised in the press but it's the first I've heard of it.

"I just find it bizarre and completely unreasonable."

Lisa Gittlemon, 38, from Park Road, Hendon, was fined twice in one day and branded the bylaw a breach of her "personal freedom".

"I should be free to put whatever I like in my car window," she said. "It's not as if I'm selling hot dogs or ice creams. It makes me furious because we're not traders. I'm going to fight it all the way."

She believes the legislation is failing to clamp down on its intended targets, traders selling a number of vehicles, because they advertise their cars in areas without parking control.

But she and others parking in pay-and-display bays have been fined after attracting the attention of parking wardens who patrol the areas.

Elaine Adeh, 52, of Hillside Drive, was fined outside a restaurant in Edgware, despite having a blue-badge displayed in her car indicating that she is disabled.

Her husband Adiz, 51, said: "We wrote to the council straight away, explaining that we're not traders, didn't know about the law and asking them to reconsider it. But they just increased it to £100.

"It's total money grabbing nonsense. Are we criminals?"

Paul Curtis, 30, of Springwood Crescent, Edgware, who was also fined, said it was "none of the council's business if I have a small sticker in my rear window".

But Councillor Andrew Harper, cabinet member for environment and transport, said: "Barnet Council does not encourage or support trading from the public highway, including offering vehicles for sale.

"This traffic order was introduced to deal with the problem of private traders offering numerous vehicles for sale from the highway.

"It would be wrong, though, for the council to take action against resident traders while not penalising other road users for breaking the rules in the same way."