The conservatives' pledge to create a minimum of 220,000 additional school places was dropped from the party's manifesto this week.
Despite the figure being included in the party's draft manifesto back in July, the promise was not included in the document released on Tuesday.
Following the launch of the manifesto Schools Secretary Ed Balls claimed the Conservatives had "quietly dropped" the target, which was to be funded by redirecting Building Schools for the Future (BSF) cash.
But a Conservative source said: "The 220,000 figure was very conservative and based on existing BSF costing of new schools.
"Given the financial situation we'll have to be a lot more inventive - using existing empty school buildings, helping providers secure leases rather than paying full up-front costs of new buildings and so on. We should be able to comfortably exceed the 220,000 (if the demand exists) while spending far less."