The statistics have been seized on by opposition politicians who say the government is "losing the war" on class sizes.

Ministers are committed to ensuring that no five, six or seven-year-old is taught in an infant class of more than 30 children, and have provided extra funding for more teachers and new classrooms.

Figures for England released by the Department for Education show that 356,388 pupils aged five to seven were in classes of 31 or more in January - a fall of nearly 130,000 on a year ago.

David Blunkett: "These figures confirm that we are on target to achieve our class size pledge"

But the number of eight to 11-year-olds being taught in classes of more than 30 has risen slightly to 835,175.

And in secondary schools, 313,586 children are being taught in classes of 31 or more - up by 31,000 on last year.

The Education Secretary, David Blunkett, described the figures on infant classes as a "substantial achievement" and said he expected fewer than 200,000 five to seven-year-olds to be in classes of more than 30 children by September.

"For the first time in 10 years we are seeing a fall in primary class sizes and an end to year-on-year increases in the number of pupils in large classes," he said.

But the Liberal Democrats' education spokesman, Don Foster, attacked the government's record on class sizes.

"The harsh reality if you are a seven-year-old is that you may be benefiting from Labour's class size policy now, but next year you stand a greater chance that the size of your class will be bigger, not smaller," he said.

"The government is painting this as a huge achievement, but in reality they are losing the war on class sizes."

'Fiddling the figures'

And the Shadow Schools Minister, Theresa May, said the government's own figures showed that class sizes for five, six and seven-year-olds had actually increased over the last four months.

"The government should be honest with people and stop fiddling the figures," she said.

Although the number of teachers employed in primary and secondary schools has increased, changes in pupil numbers appear to be contributing to the class sizes situation.

While the number of pupils in primary schools decreased by 3,500 to 4,296,900 (a fall of 0.1%) over the past year, the number of teachers increased by 1,100 to 182,500 (a rise of 0.6%) as a result of increased government spending.

But in secondary schools, although the number of teachers increased by 1,700 to 183,500 (a 0.9% rise), the number of pupils rose by 47,400 to 3,120,200 (up 1.5%) .