Worsening health among the under fives in the UK needs to be urgently addressed, experts say.
The Academy of Medical Sciences highlights what it says are "major health issues" like infant deaths, obesity and tooth decay.
It says society is betraying children and the problems are limiting their future and damaging economic prosperity.
The government says children's health is a priority.
A spokeswoman said: "We've taken significant action to improve children's health now and in the long term."
This includes measures to reduce sugar in children's food and investing in mental health services and dentistry, she added.
But the academy, which represents medical scientists and health researchers in the UK, pointed out that progress on child health had stalled in recent years.
It says the pandemic and increased cost of living was to blame - and had proved particularly damaging to those living in more deprived areas.
Its report says:
The UK is 30th out of 49 rich countries for infant mortality
One in five children falls short of the expected level of development aged two
One in five is overweight or obese by five
Vaccination targets are being missed for diseases such as measles
One in four is affected by tooth decay by five
One in five women struggles with their mental health during or just after pregnancy
Air pollution is linked to worsening asthma
Rising demand for child mental health services
The report calls for a cross-government vision to be developed to tackle the problems and investment in the child health workforce, including health visitors.
Report author Prof Helen Minnis said: "Every child has the right to a safe and healthy childhood. It is shameful that the UK is failing to provide this.
"The science is clear - we are betraying our children."
And fellow author Prof Sir Andrew Pollard said there had been an "appalling decline in the health or our children" which was creating a "bleak outlook for their future".
He added: "It is time for big thinking and clear strategy by government to protect the health and life chances of our children and transform the future of our nation."
Dr Mike McKean, of the Royal College of Paediatrics and Child Health, said the repot provided "alarming evidence".
"We are presiding over a crisis in child health that demands urgent action."
