The UK is "falling behind" comparable countries for several child health issues, a new report has found.
Improvements in life expectancy have stalled, breastfeeding rates are among the lowest in the world and the nation's children have some of the highest levels of obesity.
An analysis of UK child health measures compared with 14 similar countries also found improvements in infant and neonatal mortality rates have halted since 2013.
The report, published by the Nuffield Trust health think tank and Royal College of Paediatrics and Child Health (RCPCH), found that for both boys and girls improvements in life expectancy has plateaued since 2011.
A boy born in the UK in 2015 can expect to live to just over 79 years - broadly similar to most comparable European countries studied.
While a girl born in the UK can expect to live to almost 83 years, this is three years less than a girl born in Spain, and the lowest of all European comparable countries.
Meanwhile, the UK has one of the lowest breastfeeding rates in the world - just over a third (34%) of babies are receiving any breast milk at six months, compared with 62.5% in Sweden.
And the UK has "considerably more" overweight or obese children and young people than in other high-income countries.
In 2013, across the UK it was estimated that 26.1% of boys and 29.2% of girls aged two to 19 years were overweight or obese.
The authors said that after many years of progress, health outcomes for babies and young children in the UK are now stalling in several key areas.
However, the authors said that child health issues have improved across nine of the 16 areas examined over the past decade, including increases in cancer survival, and a rise in the rate of immunisation.
But the UK still lags behind countries like Sweden, Spain, Germany and the Netherlands on the uptake of measles inoculations.
Nigel Edwards, chief executive of the Nuffield Trust, said: "With some honourable exceptions, child health is notably absent from much policy thinking at the moment and we are now falling behind our peers when it comes to several vital measures.
"It's time for policymakers to take child health seriously before our somewhat mediocre international standing becomes even worse."
Dr Russell Viner, president of the RCPCH, added: "Given that children and young people make up a quarter of the UK population, it's a real failure of the system that child health gets so little political attention.
"We want to see the UK Government develop a comprehensive cross-departmental child health strategy, which includes a 'health in all policies' approach to policymaking.
"It's also crucial that some of the biggest threats to child health are tackled boldly; for example, tighter restrictions on junk food advertising to tackle obesity, the reinstatement of child poverty reduction targets and, crucially, the reversal of damaging public health cuts."
Eustace de Sousa, national lead for children, young people and families at Public Health England, said: "Ensuring every child has the best start in life is a priority for PHE, but we still have challenges ahead.
"We are making good progress, such as our rates for MMR vaccinations for five year olds exceeding the World Health Organisation target of 95%, and among the most ambitious plans worldwide to tackle childhood obesity.
"We also need to focus our efforts on reducing inequalities, particularly among children and families from poorer communities."
A Government spokesman said: "This Government is committed to ensuring children get the best start in life - that's why we have introduced mandatory health visitor checks, a world-leading vaccination programme and robust plans to tackle childhood obesity.
"Childhood mortality is at an all-time low, and we will continue to do everything we can to reduce the number of families who go through the tragedy of losing a child."
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