Liberal Democrats will vote on Sunday on proposals calling for the party to back controversial health reforms after a rebel bid to kill off the plans failed.

Members will be asked to back calls by Baroness Williams for peers to support the final stage of the Health and Social Care Bill.

Critics will stage a final bid to formally show their opposition to the plans by attempting to remove that pledge from the emergency motion at the Lib Dem spring conference in Gateshead. But even if successful it would not oblige the party to oppose the plans.

It means Deputy Prime Minister Nick Clegg has escaped a potentially embarrassing move to enshrine withdrawal of the Bill in party policy.

On a straight vote campaigners against the NHS shake-up won enough support yesterday to have their "kill the Bill" emergency motion debated. But, under the party's alternative vote system, they lost out to the "Shirley Williams motion" on second preferences.

The legislation was "paused" after the party's spring conference last year amid a furious backlash. It has since been amended more than 1,000 times, but many prominent health organisations remain fiercely opposed to the plans Mr Clegg insists activists will be "comforted" by the scale of the changes to the original Bill.

But he admitted his biggest lesson as leader had been the failure to convey the argument on NHS reforms.

He said: "I tell you one thing I have learnt on what could be handled better.

"I have learnt, and frankly I've learnt it the hard way over the last year and a half, you can't spring on to the public a solution or a policy if you don't spend a lot of time first explaining what the problem is.

"If we had spent more time explaining that simply having more and more people going to hospital for an increasingly long period of time is just not a sustainable way to run a good healthcare system...

"Maybe we should have spent time showing people there is a problem, because if you don't show them there is a problem first, why should people accept that there is a need for a solution?

"So I suppose that's the main lesson I've learnt."

Unison general secretary Dave Prentis said voters "would never forgive" the Lib Dems for pushing ahead with the Bill.

He said: "This is a huge disappointment for everyone that cares about our health service.

"By failing to mount a serious challenge to the health bill, the Lib Dems not only threaten our NHS but also their own survival. Support for the party is at an all time low.

"Voters will never forgive it for ignoring health professionals, patients and unions and ploughing ahead with a bill that will ruin our NHS and rob future generations of decent healthcare.

"We are running out of time but the fight to save the NHS is not over. Lib Dems in Gateshead should vote against Shirley Williams' motion which will not safeguard the health service from harm.