The Health and Social Care Bill has received royal assent to become law, after a troubled 14-month passage through parliament.
Clinical commissioning groups (CCGs) will begin an authorisation process in October to take over statutory responsibility from PCTs from April 2013.
Health secretary Andrew Lansley said: 'The Health and Social Care Act will deliver more power to clinicians, it will put patients at the heart of the NHS, and it will reduce the costs of bureaucracy.'
Ministers' announcement of royal assent came as an early version of the Transitional Risk Register, detailing the potential impact of the legislation, was leaked to NHS commentator Roy Lilley and GP and broadcaster Dr Phil Hammond.
Dated 28 September 2010, the assessment highlighted dangers associated with implementation including potential for CCGs to 'go bust' and clinical time to be lost to commissioning activity. It also warned the new system could be more expensive.
The leak prompted calls for publication of the final version of the Risk Register, which ministers have refused to reveal despite an order to do so by the NHS Information Commissioner's office.
A DoH spokesperson said: 'We have always been open about risk and have published all relevant information in the Impact Assessments alongside the Bill. As the latest performance figures show, we are dealing with those risks.'
During its passage through the House of Lords, the Bill received 328 amendments; however, health professionals continue to oppose increased competition in the NHS.
In January, an IN survey of 242 nurses found 83 per cent wanted the Health Bill scrapped; 84 per believed Mr Lansley should step down.