Around 2,000 primary schools need to be built to provide children born during a 'mini baby boom' with an education, Labour claims.
Shadow education secretary Stephen Twigg has urged the government to steer their focus away from free schools and prioritise on primaries, saying the Department for Education (DfE) is "ignoring" the crisis.
"Across England we need nearly half a million more primary places - the equivalent of building an extra 2,000 primary schools between now and the general election," Twigg said.
Some 450,000 children need to be allocated places at schools in England by 2015, according to the shadow secretary although he adds many could be accommodated in expanded primaries.
"At the moment, the government has only promised an extra 100 new free schools, many of which will be secondaries.
"The government seems oblivious to the problem, preferring to focus on pet projects rather than real need," he added.
The government attests it will pledge £4bn on easing the pressure but according to Twigg, much of the money has already been set aside for free schools.
The DfE said there are currently 444,000 unfilled primary school places nationally, "many in low-performing schools where parents don't want to send their kids".
"That's why we make no apology for intervening to drive up standards and turn them around."