The prime minister wrote in the Sunday Telegraph that an 'opt-out system has the potential to close the gap between the potential benefits of transplant surgery and the limits imposed by our current system of consent'.
The proposals were backed by Sir Liam Donaldson, England's chief medical officer, who said they would make it easier for GPs to approach grieving relatives.
The BMA said it supports the introduction of a planned system of presumed consent. Its survey of public attitudes, published in October, showed 62 per cent backed presumed consent.
At present, 90 per cent of UK residents back organ donation, but only a quarter are registered as donors.