Campaigners are bringing a judicial review of plans to create new regional Accountable Care Organisations (ACOs) to oversee healthcare.
ACOs are part of emerging plans across the country intended to help integrate NHS services, encouraging hospital and ambulance trusts, GPs, local authorities, social care providers and health commissioning groups working more closely together.
NHS England, backed by Health Secretary Jeremy Hunt, says they will help meet soaring demand in the health service, ease pressure on hospitals and provide care in appropriate and cost-efficient settings.
Opponents claim they are vehicles for privatisation and cuts to services, and will argue in court that the proposed contract for ACOs, under which care would be commissioned using a single budget, is unlawful.
The contracts could run for up to ten years and would see tens of billions of pounds awarded to NHS organisations and potentially private healthcare providers.
Under the current system healthcare providers are paid for each patient they treat, with the price determined by the complexity of the procedure.
Under the proposals ACOs would receive a single payment, known as a Whole Population Annual Payment, which opponents say may lead to rationing of care and a focus on the most profitable services.
The first ACO contracts were due to be awarded in Manchester and Dudley this month, but were effectively put on hold in January when, under pressure from concerned MPs, NHS England announced a twelve-week consultation.
999 Call for the NHS said: “[We are] deeply concerned that the contract, if implemented, would threaten patient safety and force hospitals and doctors to restrict treatment, making decisions based on money not clinical judgement.
NHS England has rejected the claim. A spokesman said: “The NHS will strongly resist this mistaken campaign to frustrate the move to more integrated care between hospitals, mental health and community services.
“The inevitable effect would be to fragment care and drive apart the very people who are now rightly trying to work more closely together on behalf of the patients they jointly serve.”
ACOs are part of a radical but largely ignored reform of the NHS directed by NHS England chief executive Simon Stevens.
He believes integrated care is the answer to the problem of rising demand in the NHS, as well as the most appropriate way of delivering the care required by an ageing population with multiple complex needs.
The aim is to relieve pressure on hospitals by providing more appropriate care in the community – either at home, at walk-in centres or other non-emergency settings – and place more emphasis on prevention to try and stem the growth of lifestyle conditions such as diabetes.
In 2014 Mr Stevens asked healthcare commissioners and providers to work more closely in 44 regional Sustainability and Transformation Partnerships, with the most closely aligned ultimately forming ACOs, with the power to commission care.
They have been characterised as an attempt to work around the shortcomings of the 2012 Health and social Care Act without legislation.
ACOs in particular have proved controversial, in part because they share characteristics, and their name, with an American model.
Earlier this year NHS England changed the terminology to Integrated Care Systems (ICSs), to try and remove the association with the privatised US model.
The judicial review may prove a more fundamental challenge to the transformation of the NHS.