Transport officials have warned motorists who smoke in their cars as they use the Tyne Tunnel they could be fined up to £200.

Newcastle Council managers, who run the tunnel, claim they are simply obeying rules that apply to other similar tunnels around the country.

But operators of the Mersey and Dartford tunnels say they have doubts about the ban and would not enforce it.

Around 40,000 motorists drive through the one-mile Tyne Tunnel every day.

The large, illuminated signs which warn drivers 'Smoking is illegal in the Tunnel' were put up at the entrance recently.

The move has been condemned by Forest, the pressure group campaigning for smokers' rights.

Spokesman Neil Rafferty said: "I've not heard anything like this before.

"It's a first as far as I'm aware.

"I used to live on Tyneside and I've driven through the tunnel many times.

"It's full of exhaust fumes and someone's cigarette isn't going to make the slightest difference.

"I would question the legality of the council's position.

"It seems to be a fanatical attitude on their behalf.

"I don't think people should break the law but, if I still lived on Tyneside, I'd be tempted to ignore this."

A spokesman for Newcastle Council said: "Technically-speaking, smoking in the tunnel has been banned since it opened in 1967.

"But, when the anti-smoking regulations came in, in July, we put up a sign to make it more visible.

"We have been responding to the complaints by drivers about customers seen putting lighted cigarettes out of the windows as they have been driving.

"It's illegal to smoke in your car in the tunnel and that is the case with all tunnels in the UK.

"The Tyne Tunnel is classed as an enclosed public space."

However, a spokesman for the Mersey Tunnel said: "The Road Tunnel Operators Association, of which we are a member, has decided not to enforce a smoking ban because it's not certain if it applies and it is also unenforceable."

A Dartford Tunnel spokesman said: "It's a grey area.

"We have no smoking signs in the tunnel but they are probably aimed more at contractors.

"I don't think there's any legislation that bans smoking in the vehicles in the tunnel and I doubt we could police it if there was."

Nobody has yet been prosecuted for smoking in the Tyne Tunnel but a council spokesman said fines for smoking in public buildings ranged from £30 to £200, depending on whether the culprit agreed to pay immediately or the case went to court.