Should private firms reimburse the NHS if they exceed a 5% profit on contracts?

Ed Miliband launched Labour’s election campaign with a promise to cap the amount of profit a private contractor can make from NHS contracts. Under the proposal private firms would be limited to profit margins of 5% on all contracts above £500,000. Proponents argue that the plan will stop the NHS’s "drive to privatisation." Opponents argue that limiting private contractor’s profits will make it harder for the NHS to keep up with rising demand for care.