A study of children in Manchester found that two in five of all three year olds had some dental decay, while in neighbouring, poorer, Salford, nearly half were affected.

Many have such bad tooth decay that they may need to have their front teeth out under anaesthetic.

The BBC's Karen Allen: "23% of all 3 year olds suffer with rampant tooth decay"

The HEA is launching a new drive to encourage child-carers and playgroups to reduce the amount of sugary food and drinks given to toddlers during the day.

Cup gives guide to dilution

They have designed a cup which helps protect young teeth by marking off the correct quantities of fruit squashes to use when diluting drinks for children.

The Greater Manchester survey, of 762 three-year-olds, found that, in Manchester itself, 40% had some dental decay.

However, one in five had evidence of serious decay, where the whole of the outside layer of tooth enamel has disintegrated.

Dentists are worried about the amount of tooth decay in young children

And half of these had the same problem affecting at least five of their teeth.

In Salford, a neighbouring city which has greater problems with deprivation, the situation was even worse.

Dr Gill Hawley, senior dental officer at Mancunian Community Healthcare NHS Trust, who carried out the survey, said sugary drinks were the number one culprit.

She said some parents sent their young children to bed with a bottle full of sugary squash to keep them quiet, causing the maximum damage to their teeth.

Experts say even natural fruit juices in a bottle can rot the teeth.

They advise never to put juices in a bottle and to phase them out after the age of one in favour of beakers.

Water and milk the only safe options

Dr Hawley said: "The only drinks that are truly safe for children's teeth are water and milk, and if you give water to a thirsty baby, it will drink it.

"Another problem is that parents won't go to the dentist until the child is in pain, by which time most of the damage has already been done."

Cathy Stillman-Lowe, the HEA's dental health campaign manager, said: "It is a sad fact that children from poor families are more likely to suffer tooth decay than children from better-off families.

"Childcarers can have a great influence on the diet of cared-for children."

The British Dental Association is calling for the fluoridation of water supplies, as there is evidence that fluoridation reduces the average number of diseased and filled teeth.

Deprivation means worse teeth

A spokesman for the BDA said: "The figures aren't surprising - it reinforces what we already know, that children in areas which are socially deprived and which don't have water fluoridation are likely to have the worst tooth decay rates."

A survey carried out last year of five year olds found that of the ten best areas of the UK, eight had entirely fluoridated water.

The average number of fillings and diseased teeth per child in England was just under 1.5, while in Wales, Scotland and Northern Ireland, it was at least 2.5 per child.