Official figures obtained by the Liberal Democrats show schools in England and Wales face a repair bill of almost pound;8 billion over the next five years to mend boilers, fix roofs and redecorate classrooms.
Phil Willis, Lib Dem education spokesman, accused the Government of diverting money from school repairs to fund flagship projects such as academies.
The figures, given in a parliamentary answer, show Birmingham has the largest backlog of repairs at pound;338 million. Lancashire and Hampshire have repair bills of more than pound;200m.
Kent has most temporary buildings (912) followed by Norfolk (837). But smaller authorities are also hard hit. Telford and Wrekin has just 84 schools but 126 temporary buildings.
Labour came to power in 1997 promising to tackle a pound;3bn backlog and has poured billions into school repairs. Capital spending on schools in England doubled between 1998 and 2004 to pound;2.6bn per year with an extra Pounds 850m of building carried out using the controversial private finance initiative.
Ministers have promised to increase total spending on school buildings to pound;6.3bn by 20078.
But, as The TES revealed last month, they have gone back on a promise that all English secondary schools will be rebuilt or refurbished by 2015. The Government now only says that by 2016, major remodelling of at least three schools will have started in every authority.
Mr Willis said: "I would never disagree that the Government has put more money in. The question is: is it focused on the right areas? People think the repair backlog has been sorted but these figures show a massive black hole in the repairs and maintenance budget.
"I would question whether building 200 academies should be the priority when hundreds of schools are looking for basic repairs." The first 17 academies to open cost a total of pound;425m to build, pound;25m each.
A Department for Education and Skills spokesman said: "We are spending record amounts to upgrade school buildings and replace temporary buildings.
"Not all temporary buildings are used as classrooms, they can be used for storage and administration. Modern temporary buildings are provided to a high specification, often to meet short-term needs."