In the space of three months, the thrust of public health policy has shifted towards a desire for individuals to take more personal responsibility for their health and the health of their children. It is a dramatic change in emphasis from the last government, sometimes accused of wanting to remove all our personal freedoms and make big decisions for us.

Health secretary Andrew Lansley took a bit of a bashing when he referred to Jamie Oliver's school food initiative as "lecturing". But he's right when he says that more of us should be taking more responsibility. The truth is that too many of us neglect our health and this is leading to increasing levels of illness and early death. The evidence is all around. There is the dramatic increase in diabetes, much of it related to obesity. Then there are the dreadful effects of excessive alcohol consumption, which we are seeing in younger and younger people.

Public health is a sensitive subject. It's not easy to strike the right balance between "protecting" people's sensibilities and telling them hard facts about their personal behaviours that are ultimately shortening their lives. Recently, I found myself on the receiving end of some vitriolic website commentary after I backed the public health minister's call for patients to be told they are "fat" rather than "obese". The Royal College of General Practitioners' call earlier this year for parents to be banned from smoking in cars carrying their children and for parents to act as role models by giving their children healthier food rather than sugary and fatty rubbish that leads to heart disease and diabetes both caused an outcry, with some even accusing me of attacking their civil liberties. I believe that parents who smoke in cars carrying small children are committing a form of child abuse; I suppose the same people also smoke at home in front of their children. Evidence from the US indicates that more young children are killed by parental smoking than by all unintentional injuries combined.

Parents really do need to take more responsibility, but this should start even before conception. Many of these avoidable deaths can be linked to low birth weight as a result of mothers smoking while pregnant. Cot death, or Sudden Infant Death Syndrome, is also directly related to smoking. Other causes of death include lung infections, burning to death as a result of fires caused by cigarettes and asthma. Women who want to conceive, or are newly pregnant, need to take more responsibility as part of their commitment to the child they hope to carry.

Obesity in pregnancy is also increasing and this is a very worrying trend. Parents need to act as role models from early on and take control of their children's eating habits by providing sensible, appropriate portion sizes and by not feeding them rubbish. You only need to look at children being fed junk in the name of convenience. I like Jamie Oliver, and I am very sad that his initiatives have failed, but unless parents exert more control over their children's diets, they are risking a lifetime of health problems and even premature death – death before their parents, which is almost too sad to contemplate.

I would also add self-induced overexposure to the sun and excessive use of sunbeds to the list. With over 100,000 new cases diagnosed each year in the UK, malignant melanoma has increased more than any other common cancer in the UK over the last 30 years – it's a really nasty killer. I admire Girls Aloud's Nicola Roberts and her campaign against sunbeds, but still you see children out in the middle of the day without adequate protection from the sun. Parents really must do more to protect children by practising safe sun protection and by being good role models.

Too many people do not face up to the hard facts, as they perceive them to be an attack aimed, in particular at the poorer members of our society. But it is impossible to argue on medical or ethical grounds that such behaviour is acceptable. GPs are not spoilsports. We genuinely want people to be able to live healthy, fulfilling and productive lives. But every day we are confronted with the harm caused by smoking, excessive alcohol consumption and obesity.

The roles for GPs are increasing. Every consultation is an opportunity to detect early-warning signs that prevent illness and disease. Sensible, timely and appropriate interventions can help make people aware of the potential risks they are taking. The Big Bolton Health Check is a great example. Since 2008, it has been offering free health screening to over-45s. More than 900 cases of potential diabetes and more than 2,000 people at high risk of heart disease have been identified who might previously have gone undetected. The initiative is also having a serious impact on reducing smoking rates and bringing down the number of admissions to hospital.

The combination of evidence and example may be the solution. I practise a patient "mantra" of give up smoking, cut down on your drinking, eat more healthily and exercise regularly. I still have patients asking for liposuction and gastric bands on the NHS because media personalities have made surgery more acceptable than common sense. At least it shows that some people want to take control of their own lives, but it would be better if people didn't become fat in the first place. Ask a parent to give up smoking and they might refuse – but demonstrate how smoking at home will damage their children's lungs, leading to bronchial illness, asthma and a lifetime of ill health and they might start to see things differently. Similarly, drinkers who are confronted with the reality of their consumption might be spurred into cutting down rather than if they were just told to do it.

I'm not suggesting that the GP profession can singlehandedly turn the situation around but we are certainly ready to play our part. Inspiration and support can sometimes come from the least unlikely quarters, as I discovered as a judge on the chief medical officer's awards. The Food Dudes programme encourages primary school age children in Wolverhampton to eat more fruit and vegetables. As well as having a dramatic effect on the children's eating habits – fruit consumption is up 54% and vegetable consumption by 48% – the local supermarkets have been forced to increase their stocks of healthy food and the parents' diets are changing too.

The StreetGames charity is inspiring young people in 20 of the most deprived communities in England and Wales to get active in dance, sport, and cycling. It has recruited 3,000 leaders and 3,000 volunteers to act as mentors in their neighbourhoods and 2 million young people aged 10-18 years are expected to take part by the end of 2010.

So please don't take offence if we tell you to lose weight or stop smoking or drinking. You need to face facts and take responsibility. Support is out there and it could save your life – and save the NHS a fortune.