They are also becoming more obese and less happy, the party said.
Keir Starmer revealed the grim data as he unveiled Labour’s plan to “create the healthiest and happiest generation of children ever in Britain”.
The height of the average British five-year old girl has fallen by 27 places in international rankings over the last three decades, Labour said, with the average five-year-old boy falling by 33 places.
The UK is also estimated to have more obese children than France, Germany, Poland and Slovenia.
And 43% of British children do not believe their life has meaning and purpose, with just 20% reporting high satisfaction with their life as a whole.
Starmer said the findings were “the reality of Tory Britain”.
Under Labour’s “child health action plan”, junk food TV ads would be banned after the 9pm watershed and every primary school will have a breakfast club.
Ads for vapes which appeal to children will also be axed, while a national supervised toothbrushing programme for three-to-five-year-olds would also be introduced.
Other measures include recruiting more staff to cut waiting lists for child mental services and delivering two million more paediatric operations, scans and appointments.
Starmer said: “Tooth decay, stunted growth and stalling life expectancy should be consigned to the history books, but instead they’re the reality of Tory Britain.
“The biggest casualty of the short term sticking plaster politics of the last 14 years are our nation’s children. My Labour government will turn this around.
“Healthy, happy children is not a nice to have, it’s a basic right, with economic urgency. We want the next generation to be chasing their dreams, not a dentist appointment. They should be aspiring to reach their potential, not reach a doctor.
“Labour will end the scandal of children being held back by poor health and regional inequalities, by slashing waits for mental health treatment and hospital appointment, putting prevention first, and fixing NHS dentistry.
“That’s the future our children and young people deserve, and that’s the future a Labour Government will deliver.”
But public health minister Andrea Leadsom said: “Given Sir Keir Starmer’s ‘blueprint’ for the country is a record of failure, he should focus on fixing his own house before criticising others.
“In Wales, Labour is overseeing the longest hospital waits in Great Britain, are the only administration to have cut the NHS budget since 2010, have underfunded the NHS and consistently fail to meet targets.
“Labour’s unfunded promises on healthcare in England would cost taxpayers billions, in addition to the £28 billion a year by 2030 spending promise they have already committed to and would inevitably hike up taxes to fund.”