The Government will take the first step on Wednesday to passing controversial legislation that will lead to more than 150 NHS organisations being scrapped.
The Health and Social Care Bill has attracted widespread criticism from unions and policy experts worried that the reforms are "too much too soon".
Under the plans, GPs will be handed the bulk of the £100 billion health budget to buy-in services for patients and a new NHS commissioning board will oversee the process.
All of England's 152 primary care trusts (PCTs) will be scrapped alongside 10 strategic health authorities.
PCTs are already being streamlined into "clusters" as part of the transition, with the aim of getting them to work with GP practices and emerging "GP consortia".
The NHS commissioning board will formally establish consortia from April 2012 but experts have warned that PCT staff are already leaving in droves, leading to concerns about patient services in the interim.
Leaders of major health unions have also queried how the NHS will implement the changes at the same time as finding £15 to £20 billion in "efficiency savings" - something no major health service has ever managed.
Doctors' and nurses' leaders have joined unions in warning that plans to create greater commercial competition between the NHS and private firms are "potentially disastrous".
A strongly worded report from MPs on Tuesday said the Government's plans introduce "significant institutional upheaval" without really changing its aims.
