She said: "I think if I was sitting in a major bank knowing that these supply companies were fleecing our schools, I would accept my moral imperative to intervene on behalf of the education sector."

However, Stephen Sklaroff, chairman of the Finance and Leasing Association, said it was up to the schools to make sure they were not signing bad deals.

The BBC has discovered that banks have large amounts invested in school leases - estimated to be approximately £300 million worth across the UK.

Panorama's 'Reading, Writing and Rip-offs' is due to air on BBC One tonight.