Under the original plans, it was envisaged that benefactors would contribute around pound;2 million towards the construction of the schools.

But funding agreements signed with sponsors show few are investing that much. The United Learning Trust, an Anglican charity, is paying just pound;1m towards the pound;30m Walthamstow academy in north-east London. It is contributing pound;1.5m towards two others, which cost more than pound;31m and pound;25.5m respectively.

Lord Harris of Peckham, the carpet millionaire, is investing pound;500,000 in two academies in south London and pound;1.5m in a third. Only seven out of 19 academies have contributed the full pound;2m, although several of the agreements fail to state how much sponsors are paying. Ministers say sponsors will in future contribute money towards educational programmes over time, rather than an upfront investment in buildings.

The most expensive of the academies opened this September is the pound;34.2m Petchey academy in Hackney, which is sponsored by the Petchey Foundation, an educational trust.

Controversy has surrounded some building programmes, including one in Greenwich where builders downed tools following a row over a funding shortfall. But the new standard contract says if costs are overrunning, both parties will consider how to reduce them, if necessary by amending the academy’s specifications.