The coalition faces renewed tensions over its planned NHS reforms this week when MPs consider the revised package.
Despite a series of concessions designed to assuage critics earlier in the summer, Liberal Democrat concerns about the Health and Social Care Bill remain. Party grandee Baroness Williams said the battle was "far from over".
Amid widespread anger at the reforms among NHS professionals and patient groups, the Government conducted further consultation and announced revisions to the Bill in June.
Changes included including hospital doctors and nurses - not just GPs - on new commissioning consortia and scrapping an April 2013 deadline for the new boards to take over.
But Deputy Prime Minister Nick Clegg still faces the prospect of a Lib Dem revolt when Tory Health Secretary Andrew Lansley brings the Bill back before the Commons on Tuesday.
In an article for The Observer, Baroness Williams said: "Despite the great efforts made by Nick Clegg and (Lib Dem Health Minister) Paul Burstow I still have huge concerns about the Bill. The battle is far from over."
She claimed there was still a legal doubt over whether the Bill would require the Secretary of State for Health to deliver a "comprehensive health service for the people of England, free at the point of need". The peer said she also still had concerns about the role of the private sector under the reforms.
"I am not against a private element in the NHS, which may bring innovatory ideas and good practice, provided it is within the framework of a public service - complementary but not wrecking.
"But why have they tried to get away from the NHS as a public service, among the most efficient, least expensive and fairest anywhere in the world? Why have they been bewitched by a flawed US system, which is unable to provide a universal service and is very expensive indeed?"
Unions this weekend renewed their campaign against the reforms, organising protests across England. Candlelit vigils and demonstrations were being held, petitions organised and street stalls mounted in towns and cities over the weekend.