The first phase of controversial legislation that will see all of England's 152 primary care trusts axed with 10 strategic health authorities is being published by the Government.
The Health and Social Care Bill has been widely criticised by union chiefs and health policy experts who are worried that the radical reforms are "too much too soon", while some MPs say the plans have taken the NHS by "surprise".
The draft legislation will outline plans for the bulk of the £100 billion health budget to be controlled by GPs, who will buy in services directly, while the whole process will be overseen by a new NHS commissioning board.
Existing primary care trusts are already being streamlined into "clusters" under the proposals, which will work alongside GP practices and an emerging network of "GP consortia".
The consortia will be formally established by the new NHS commissioning board from April next year, but experts say many staff are already quitting primary care trusts, leading to concerns about the impact on patient services over the next 12 months.
Health union chiefs are also concerned about how the NHS will be able to implement the changes while making £15 to £20 billion in "efficiency savings" by 2014, and warned of the "potential disaster" of creating greater commercial competition between the NHS and private firms.