Passions have been stirred after the NHS East of England put forward proposals to invite competitive bids for an "operating franchise" to run the hospital which serves 160,000 residents.

Organised by the country's biggest health union, UNISON, a demonstration will assemble at noon at Riverside Park, Cambridge, and march on through the city. A rally at Hinchingbrooke itself with follow at 1.30pm.

The news comes as UNISON publishes a report called Up for Grabs in response to the proposal which has been put forward as the preferred option in a consultation on the future managing of the site.

The union said the proposal was "highly controversial", and accused the NHS of discussing the matter "in secret", claiming that local people "will be the last to know" when a decision is actually made.

However, the NHS East of England today blasted back at UNISON saying "the accusation of 'up for grabs' is nothing but scaremongering".

Hinchingbrooke currently faces a cumulative deficit of £38.7 million and reducing levels from Cambridgeshire Primary Care Trust, which means no NHS organisations can afford to take it on as a going concern.

However, according to UNISON, any private sector involvement would require "hefty 'sweeteners', generous profit margins and guarantees to compensate for any risk".

UNISON regional organiser Phil Green said: "It really is a scandal that the future of services in the area is being discussed behind closed doors excluding the press, the public and NHS staff whose jobs are potentially at stake.

"It's clear the SHA (Strategic Health Authority) have closed their minds to anything but franchising. They are obsessed with using the private sector, no matter how expensive, inappropriate and useless it may turn out to be."

However, a spokesman for the NHS East of England said that services at Hinchingbrooke were safe. He said: "What we are discussing now is how we can find the right partner to provide those services, which will guarantee a safe, sustainable future for Hinchingbrooke.

"Whichever option is taken forward we have been clear from the outset that the staff, buildings and assets will all remain within the NHS. That has been clear from minute one, day one of this process and remains the case now.

"The discussions about the future of Hinchingbrooke are anything but secret; we have presented progress to the local council's overview and scrutiny committee three times in the last six months.

"No decision has been made. We have options on the table and we will be engaging the staff, unions and the public in ensuring we get the best deal for patients and the NHS."