It was clear before the general election: should the Conservatives win, the nutrition section of the Food Standards Agency would be transferred to the Department of Health, where ministers could have tighter control. However, I am scandalised by how quickly and how far Andrew Lansley, the health secretary, is handing public health over to the food and alcohol industries.

The sabotaging of public health by the food industry is universally recognised. When I was involved in establishing the FSA for Tony Blair in 1997, it became clear that ministers were under intense pressure from the food industry to exclude nutrition and focus solely on food safety. Later that year, when I produced a report for the government on the prevention of childhood obesity, the then minister of public health, Tessa Jowell, told me my proposals were extraordinarily radical because I suggested advertising and marketing might influence children's behaviour.

She said food industry representatives wished to speak to me. Within days I was invited to dinner at the Food and Drink Federation, where I was attacked by several chief executives who considered it entirely reasonable to market products directly to children. They resented my proposal not only to transform school meals, but to take measures to restrict the tens of millions of pounds of confectionery and soft drinks bought by children. Our obesity report was never published, but all its recommendations have been accepted by many governments, as well as the World Health Organisation and NGOs around the world.

The FSA, with its magnificent analyses of the impact of food advertising on children and its traffic-light labelling system for packaged foods, has been considered the premier initiating public health body in the world. Its independent approach is particularly needed now that obesity has become the third most important risk factor for health – after tobacco and alcohol – in the affluent world.

Despite all this evidence, the FSA's nutrition role was rapidly transferred after the election to the health department – to the delight of the food industry. Now we learn that policymaking is being directly handled by firms within the industry, including McDonald's, PepsiCo and Kellogg's. Maximising profit remains their core purpose, with public health assigned to an enigmatic "corporate responsibility" agenda.

Obesity ballooned in the UK in the mid-80s when the food industry realised that intense marketing, particularly to children, profoundly influences purchases. Senior executives of large European food firms have told me that once they have a reasonable product, they lower the price, make it easily available, and use sophisticated and intense marketing to increase sales.

It is also been recognised by the WHO and others that the poorer members of society are much more likely to purchase cheap foods which therefore contain abundant amounts of fat, sugar and salt. This is a huge health burden.

The British food industry was pushed by the previous government to start reducing the salt content of food products, but, as in many other countries, it only began to do so when threatened with regulatory measures. The current government is now reversing the lessons of the last 10 years about what is necessary for improving public health.

David Cameron has said that obesity is everybody's individual responsibility. Lansley's reforms are the embodiment of that view. Thus the government is now flying in the face of all the scientific and public health evidence on what needs to be done, as set out by the chief scientist in 2007. It is a major setback for the health of the nation.