The British Dental Association says dental health inequalities across the country could "go from bad to worse" after the coronavirus pandemic if the Government does not support services which have faced disruption.
Public Health England data shows that 21.1 per cent of children surveyed in North East Lincolnshire over the last two school years had experienced some form of dental decay.
That was among the highest proportions of the 101 local authority areas for which figures were available, but the health body cautioned that this was based on a small number of children examined – 62 were included in the survey.
Where decay was reported, the youngsters had an average of two rotten teeth.
Figures also show the oral health of pre-schoolers in North East Lincolnshire has declined since the survey was first carried out by PHE in 2013. That year, 15 per cent of children had tooth decay.
Those surveyed in 2019 and 2020 were among 1,500 three-year-olds across Yorkshire and The Humber to be examined, where 14.7 per cent of children had rotten teeth on average.
Across England as a whole, 10.7 per cent of three-year-olds had reportedly experienced tooth decay, the report revealed.
The data, drawn from a sample of almost 20,000 three-year-olds from across the country, found wide regional variations.
Pre-school age children living in Yorkshire and The Humber were more than twice as likely to have experience of dental decay than children living in the East of England (6.7 per cent).
The authors of the report wrote: “Dental decay is largely a preventable disease.
“Poor oral health impacts on children and families affecting children’s ability to eat, smile and socialise and causing pain and infection with days missed at nursery, and for parents work, to attend the dentist and hospital to have teeth out.”
The British Dental Association says tooth decay is the number one reason for child hospital admissions nationally.
Eddie Crouch, BDA chairman, said: "In a wealthy 21st century nation there's no reason why decay and deprivation still go hand in hand.
"Sadly, millions of missed appointments, lockdown diets and the suspension of public health programmes mean things are set to go from bad to worse when it comes to health inequality.
"It's time for real commitment from the Government if we're going to avert an oral health crisis."
Mr Crouch added that ministers must offer support for services "facing a deeply uncertain future" to prevent an oral health decline.
A Department of Health and Social Care spokesperson said: “The Government is committed to the effective measures to improve the oral health of children, which is why we will be consulting on supervised toothbrushing and removing barriers around water fluoridation.
“We have also taken significant action to reduce the sugar content in food and drink almost 44% of sugar cut from drinks thanks to the Soft Drinks Industry Levy."
They added that a new NHS rule requiring dental practices to hit 60 per cent of their pre-COVID activity until October "is expected to improve access to vital dental services and target groups with the highest needs".