Children are failing to learn to read and add up because they are being sent to formal school too young, the seminar heard.
The senior Labour figure said: "We have too many four-year-olds in schools and there is a growing body of evidence that we have got it badly wrong. Is there a link between poor literacy and forcing kids to start school too young?"
In countries such as Hungary, Switzerland and Flemish-speaking Belgium which were more successful in teaching literacy and numeracy than Britain, formal teaching of the three Rs did not start until children were six or seven.
Before six or seven they had a structured curriculum but it did not include reading, writing or arithmetic. They were taught skills such as speaking, paying attention, listening, using their memory and motor skills, said the figure, who cannot be named because of the rules governing the seminar.
In Switzerland, parents can choose not to send their children to school at six and 15 per cent wait until they are seven.
By next September, the Government has promised, every four-year-old will have a nursery, playgroup or school place. Local authorities are drawing up plans to achieve this, but first signs are that most four-year-olds will continue to be taught in reception classes. The Department for Education said yesterday that a quality assurance consultation on all early years provision would take place in the New Year.
Ministers are piloting early years centres of excellence which will bring together services for the under-fives.
One expert at the seminar said that other countries such as New Zealand which began reading early tended to have the same difficulties as Britain: a wide gap between children at the top and bottom and poor performance in literacy and numeracy.
Some of the worst offenders were independent prep schools. "They try to get on with these things far too early. Lots of children are damaged and have to be catered for in the state system."
During a discussion on private schools, the senior Labour figure, who supports most of the Government's education initiatives, urged ministers to use the threat of the removal of charitable status as a stick with which to beat private schools.
Two weeks ago, ministers announced a new partnership with independent schools and promised not to support the removal of charitable status.
The figure said: "I would go much tougher than the Government on charitable status. Charitable status goes back to 1603 when all education had a charitable purpose. Now that we have universal state education we have to question whether it remains relevant."
Ministers have emphasised that private schools will not be forced to form partnerships with state schools though they hope some private schools will help prepare some state school pupils for Oxbridge and in minority subjects.Reuse content