Peers have fired an early warning shot across the government’s bows over controversial health care reforms.

The Health and Social Care Bill, implementing the NHS shake-up, cleared the Commons earlier this week but faces an uphill battle in the Lords.

Even before detailed scrutiny begins next month, peers have served notice of the changes they will demand.

Leading the charge, Labour’s Baroness Wheeler said it was still not clear why this “massive upheaval” was needed.

She said health professionals remained deeply concerned about the “destabilising” effect the reforms would have on the NHS.

And she insisted that MPs had failed to resolve issues surrounding the health secretary’s duties and role.

Lady Wheeler poured scorn on Liberal Democrat claims to have won major concessions from the coalition government in the “listening exercise” that came during a pause in consideration of the Bill.

The “scorecard result”, she suggested, was “far more modest” than Liberal Democrat leader Nick Clegg had claimed.

The Bill would add more layers of bureaucracy and increase costs, with “increasing complexity” likely to slow down decision-making.

Her comments came as peers debated the implementation of recommendations made by the NHS Future Forum, which oversaw the listening exercise.

Following the exercise the Bill was sent back to committee in the Commons for a series of revisions, including giving health professionals other than GPs power over how NHS funds are spent, stronger safeguards against a market free-for-all and scrapping a 2013 deadline for the introduction of new commissioning groups.

But as well as facing opposition from Labour and creating concerns for the unions and medical royal colleges, the plans have also exposed fault lines within the coalition.