Poll: Should there be a complete ban on smoking in cars?

The ban across England follows a similar one brought into force in Wales following experts' warnings about the dangers of second hand smoke.

From today it is an offence for a person of any age to smoke in a vehicle that is carrying someone who is under 18 years old. It will also the driver's responsibility to stop any passenger smoking in these circumstances.

If caught, both the driver and the smoker would be fined.

There are anomalies – the law does not apply if the driver is 17 years old and is on their own in the car – and there is also a lack of enthusiasm from police officers in having to enforce a new law.

Russell Yeomans, chairman of West Mercia Police Federation, today welcomed the introduction of the new legislation.

But he also warned that cuts in policing numbers are already putting a strain on the force.

He said: "At a time when police officer numbers are being cut nationally and there are cuts to police budgets, this is just another piece of legislation we are expected to enforce.

"This is at a time when officer numbers are falling and I wonder whether they will be able to enforce it while other demands are increasing."

Shocking figures were released today to coincide with the ban on smoking in cars with children.

Scientists have shown the harm second-hand smoke poses to youngsters – even with the windows down.

Dr Anil Namdeo, of Newcastle University's Transport Operations Research Group, has carried out experiments on second-hand smoke in vehicles to test levels of dangerous chemicals – fine particles 100 times thinner than a human hair known as PM2.5 – which children sitting in the back of a car would breathe in.

His team tested having the windows open or closed, fans on or off and with the air recirculating or not.

Drivers tested 20 minute routes around Newcastle, replicating a school run, using volunteer smokers. Dummies were used in the back as no children were involved.

Despite common misconception, even driving with the windows open while smoking exposed those in the back to dangerous levels of chemicals.

The test found even with the window open, levels were more than 100 times higher than recommended safety guidelines.And with windows closed and the fans on, levels were more than 200 times the safe limits.

Levels of poisonous carbon monoxide were two to three times worse than on a busy road at rush hour.

Professor Kevin Fenton, National Director for Health and Wellbeing for Public Health England, added: "This experiment unearths shocking data, reinforcing that smoking in vehicles with a child is never safe. Even with the window down you are still putting your child at risk of developing serious health conditions."

Children are more susceptible to the effects of second-hand smoke, as they breathe more frequently than adults and their respiratory systems and immune systems are still developing.

Second-hand smoke contains 4,000 chemicals, more than 50 of which cause cancer. Experts think three million children are currently exposed to it, putting them at risk of serious conditions including asthma, bronchitis and infections of the chest.

Dr Namdeo said: "People think that by opening the window they are clearing the air, but what actually happens is the air is sucked in from outside and pushes the smoke backwards, straight towards the passengers in the back seat."

Mr Yeomans said police are facing difficult choices over their priorities, something he feels the public understand.

He said: "I wonder if it is, or if it should be a priority for the police force in these times of austerity? I understand why it is important that people do not smoke in cars with children. We are in agreement with these laws and it is a well intentioned law, but I just wonder with the amount of extra work police officers are already expected to do, how much time they will be able to put on it."

Figures from the Lung Foundation show that around 185,000 children between the ages of 11 and 15 in England are exposed to potentially toxic concentrations of second-hand smoke in their family car every day or most days - the equivalent of more than 6,100 classrooms full of children.

It is an issue that has concerned health experts for decades and today's law is an extension of rules banning smoking in public.

Police and local authorities have been told they are able to enforce the law immediately, but in reality they are thought to favour a period of educating drivers rather than enforcement action.

A National Police Chiefs' Council spokeswoman said: "As the existing smoke-free law extends to vehicles, police forces will be following guidance from the Chartered Institute of Environmental Health by taking an educational, advisory and non-confrontational approach when enforcing the new legislation.

"Local authorities enforce the existing legislation and police forces are included as enforcement authorities for the new offences.

"During this period, individual offences that justify enforcement action will be reported to local authorities."

Jack Dromey, the shadow policing minister, today welcomed the law – but lay the pressure placed on police at the door of the government.

He suggested the police's approach was more about constabularies saving money at a time when their budgets are being slashed.

Mr Dromey said: "The ban on smoking with kids in cars is designed to protect their health and save lives. It is absolutely wrong that Theresa May's police cuts will put vulnerable children at risk."

A source at the Department for Health admitted that the expectation was not that the police would begin proactively hunting for those flouting the law and said the intention was that the legislation would underline a "cultural change" in the habits of motorists who smoke.

The source said: "We do not believe that anyone wants to poison their children through second hand smoke and like other smoking campaigns we hope there will be a change in the way people behave."

The source added: "We will not be measuring the success of this campaign by how many fines are handed out.

Smoking groups have welcomed the new measures, which are designed to reduce the risks caused by second-hand smoke. Polls also show that the overwhelming majority of people in England also back the ban.

A ban on smoking in cars carrying children is already in place in some states in America, Australia, Canada and a few countries in Europe.