The number of primary pupils in classes of more than 30 grew by 80,000 between January 1994 and January 1995, the Government admitted this week.
Official figures obtained by Don Foster, the Liberal Democrat education spokesman, reveal that at the beginning of the year there were 1.15 million youngsters in classes that exceeded 30.
The sharpest increase came in the London borough of Newham where an extra 1,363 children found themselves in large classes - an increase of 103 per cent on the previous year.
The figures, which are provisional, cover the period before this year's round of education cuts which, governors say, have led to the loss of more than 4,000 teaching jobs. An extra 86,000 pupils started school last month.
Mr Foster said: "While the debate about whether class size matters or not goes on, actual class size is relentlessly rising."
Since 1992 there has been a 28 per cent increase in the number of children in classes of 30 or more. In the past year there was a 7 per cent rise. There are now five education authorities where more than half of primary-aged children are taught in such classes (see box below).
"Classes of more than 30 are nonsensical," said Mr Foster. "Children are not getting their fair deal, they are getting short changed. Teachers are over-stressed and unable to give a reasonable amount of time to individual pupils."
The Liberal Democrats have said they will invest Pounds 2 billion in education but have no limit on class size.
Labour has pledged to use money obtained by abolishing the Assisted Places Scheme to cut primary class sizes.
In contrast, the Conservatives have said there is no evidence that large classes affect pupil performance.
The figures reveal that London authorities have suffered the most from burgeoning classes. There was a 50 per cent increase in the number of children in classes of more than 30 in the boroughs of Hammersmith, Kensington, Westminster and Richmond.
Among the metropolitan authorities the highest rise was in Coventry where 2,334 more children were in classes exceeding 30. In the counties, North Yorkshire saw a 30 per cent rise.
A spokesperson for the London borough of Newham said: "We expect that much of the increase relates to population pressures rather than school organisation or budgetary measures. Indeed there have been no cuts in delegated budgets in that period. And we still have relatively few children in classes over 30 compared to many LEAs."