And ministers are claiming victory in the battle against large classes by beating their own target of reducing the figure to 50,000 by September.

Last year, 11 per cent of five, six and seven-year-olds in England were in classes of 30-plus. The figure was 22 per cent in 1998.

Thirty-nine local authorities have no children in large classes but 10 still have more than 700 pupils in classes of more than 30.

Essex has the highest number at 1,523 but started at 11,051 in 1998. Leicestershire has nearly a quarter of its 1998 total of 4,407 pupils in 30-plus classes.

A total of pound;73 million will be made available next year to reduce class sizes for eight to 11-year-olds. The number of pupils in classes over 30 is already falling and the pupil:teacher ratio is improving for this age group, after rising for a decade.

Mr Blunkett said: “When we came to power almost half a million infants were being taught in classes of over 30. This was making it harder for teachers to teach the basics effectively.”

He dismissed claims that secondary-school class sizes were a problem, noting that the averge class was 22 pupils. More than 92 per cent of secondaries have classes with 30 or fewer pupils.

Mick Brookes, president of the National Association of Head Teachers, said in some cases reducing class sizes at key stage 1 had increased class sizes in the later primary years.

“While it is good news for infants, the Government must now look at key stage 2 and 3 and avoid the kind of bureaucracy they managed to create with their infant class-size pledge.”

John Dunford, general secretary of the Secondary Heads Association, said: “The Government will go into the next election having presided over an increase in secondary class sizes during a period when its top priority has been education.”

Tory education spokeswoman Theresa May claimed the number of secondary pupils in classes over 31 had risen to 334,153 - a 36 per cent rise - under Labour.

Phil Willis, Liberal Democrat spokesman, said: “For all the Government’s claims, the average size of classes for eight to 11-year-olds is still higher than in 1997 when Labour came into power.”

Welsh class size figures will be released in two weeks. The assembly will spend pound;65m over three years recruiting more teachers to reduce class sizes at key stage 2.