Tony Blair was today trying to save plans to transform a Mid Sussex hospital into a super NHS Trust amid fears of a massive backbench revolt.
The Prime Minister was outlining the case for foundation hospitals in a speech on public sector reform in London.
Mr Blair was set to deny the policy would create a "two-tier" NHS - with Queen Victoria Hospital, in East Grinstead, poaching staff from local hospitals which do not have the special status.
The Prime Minister, speaking on his 50th birthday, will also warn critics it would be a huge mistake to turn their backs on reform.
His intervention came ahead of a crucial Westminster vote on the policy tomorrow.
The Government is braced for as many as 130 Labour MPs to vote against the proposal, which is also fiercely opposed by the Liberal Democrats.
Leading rebels include Brighton Kemp Town's Dr Des Turner, who has already held talks with Mr Blair at Downing Street.
He has accused Mr Blair of trying to do something "not even Margaret Thatcher" attempted - the effective privatisation of the NHS.
He said: "I regard the foundation trust idea as a betrayal of the NHS ethos we have all fought for. This could get very serious indeed."
Mr Blair could face a bruising defeat if the Tories vote against foundation hospitals.
Health Secretary Alan Milburn today also stepped up efforts to limit the size of the rebellion.
He has pledged to resign if patients end up having to pay for treatment in the new hospitals Ministers will also release a document, the NHS Improvement Programme, which details how they intend to help all hospitals in England to achieve foundation "three-star" status within five years.
A fund of £200m will be available along with support for managers for those hospitals judged to be below the required standard.
Speaking on the release of the NHS Improvement Programme, Mr Milburn said: "This is a policy for all and not just for some. "It is not about elitism or two-tierism. It is about levelling up, not levelling down."
In Sussex only the Queen Victoria Hospital is currently in line for special status because it was the only one to achieve the top "three-star" rating in performance tables.
However, the Government has said it eventually wants all hospitals to become "super" trusts.
Health Secretary Alan Milburn insists the changes would help improve standards across the NHS.
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