A leading public sector union has launched legal action against the government, claiming ministers failed to consult over plans to "fundamentally change" the way the NHS is run.
The shake-up of services was set out in a health White Paper published in July.
Unison, which argued the reforms represent the most fundamental change to the way the NHS operates since its creation, said it intends to challenge Health Secretary Andrew Lansley over his "refusal" to consult on the plans.
Unison also claimed NHS Chief Executive, Sir David Nicholson, wrote to all NHS chiefs instructing them to start implementing the proposals "immediately" the day after the White Paper was published, which it maintains was unlawful.
Officials argued that no steps should have been taken to implement the changes until the public had been given the opportunity to comment on them.
Karen Jennings, Unison's Head of Health, said: "I find it incredible that the NHS chief executive would say he believes there is no legal duty on the secretary of state to consult on the merits of the proposals in the White Paper."
A Department of Health spokesman said: "The White Paper sets out a clear strategy and sustainable structure for the long-term future of the NHS. It gives NHS staff and the patients they serve a clear sense of direction and purpose. The Government is engaging fully with the public, healthcare professionals, local authorities and unions on how its proposals will be implemented."