Cost-cutting plans that could lead to A&E and hospital closures are being kept secret from the public, a leading think tank has warned.
NHS England has told local health officials not to reveal the plans to the public or the media before they are finalised and have been approved first, according to published documents and new analysis by the King's Fund.
The public body even told local managers to refuse applications from the media or public wanting to see the plans under the Freedom of Information Act.
Health officials in 44 areas have been ordered to draw up the strategies setting out how they will cut costs and improve care in the wake of a record £2.45 billion deficit.
The sustainability and transformation plans (STPs), some of which have already been published or leaked, could see services like A&E units, maternity units or even whole hospitals close, with other services being merged.
NHS England say the changes will improve patient care and are necessary to fulfil Health Secretary Jeremy Hunt's plans for full seven-day services.
Campaigners argue that these measures are just a way of cutting services.
Some councils have objected so strongly to being told to keep plans secret that they have ignored NHS England's demands and have published them on their websites.
The new report from the King's Fund said that NHS England had set tight timescales which is partly why doctors and patients have been shut out of the process.
It said: "It is clear from our research that STPs have been developed at significant speed and without the meaningful involvement of frontline staff or the patients they serve.
"Patients and the public have been largely absent from the STP process so far."
One local health manager said: "I've been in meetings where I've felt a little bit like, you know, 'where are the real people in this?'" while another said the secrecy demanded by the public body was "ludicrous".
The report said: " As well as the timeline creating a barrier to meaningful public engagement, national NHS bodies had also asked STP leaders to keep details of draft STPs out of the public domain.
"This included instructions to actively reject Freedom of Information Act requests (FOIs) to see draft plans. Two main reasons were given for this.
"The first was that national NHS leaders wanted to be able to 'manage' the STP narrative at a national level - particularly where plans might involve politically-sensitive changes to hospital services.
"The second was that national leaders did not want draft proposals to be made public until they had agreed on their content."
However, the King's Fund said that STPs still offered the best opportunity to improve health and care services.
Chris Ham, chief executive of the King's Fund, said: "The introduction of STPs has been beset by problems and has been frustrating for many of those involved, but it is vital that we stick with them.
'For all the difficulties over the last few months, their focus on organisations in each area working together is the right approach for improving care and meeting the needs of an ageing population.
"It is also clear that our health and care system is under unprecedented pressure and if STPs do not work then there is no plan B."
NHS medical director Professor Sir Bruce Keogh defended the plans, saying: "Advances in medicine also mean it is now possible to treat people at home who would previously have needed a trip to hospital.
"It also means those with the most serious illness need to be treated in centres where specialist help is available around the clock.
"So, this is not a moment to sit on our hands. There are straightforward and frankly overdue things we can do to improve care."