London - Every child in the world is under threat as decades of health improvements begin to stall, according to major World Health Organisation report.
Obesity, air pollution and climate change pose an "immediate threat" to children in wealthy and poor countries alike.
The World Health Organisation is an arm of the United Nations. Its report, written by 40 experts from around the world and published in the Lancet, blames big business for "exploitative marketing practices" to "push heavily processed fast food, sugary drinks, alcohol and tobacco at children".
Globally, the authors are most concerned about environmental issues and obesity.
They believe "predatory marketing" of junk food and sugary drinks is directly driving obesity – the number of obese children and adolescents globally having increased from 11 million in 1975 to 124 million in 2016.
Professor Costello said: "Industry self-regulation has failed. Studies have shown that self-regulation has not hampered commercial ability to advertise to children."
Helen Clark, former prime minister of New Zealand, who co-chaired the report, said: "Despite improvements in child and adolescent health over 20 years, progress has stalled, and is set to reverse. Every child worldwide now faces existential threats from climate change and commercial pressures.
"Countries need to overhaul their approach to child and adolescent health, to ensure that we not only look after our children but protect the world they will inherit in the future."
Dr Tedros Adhanom Ghebreyesus, director-general of WHO, said: "This report shows that the world’s decision makers are failing today’s children – failing to protect their health, their rights and their planet.
"This must be a wake-up call for countries to invest in child health and development, ensure their voices are heard, protect their rights, and build a future that is fit for children."