A decision on whether to close an emergency department at a major hospital is being driven by the "wrong priorities", Ed Miliband has said.
The health secretary, Jeremy Hunt, will make a Commons statement at around 11.30am on Thursday on whether the newly revamped A&E department at Lewisham hospital in south-east London will be replaced with an "urgent care" ward, and its maternity services turned into a midwife-led unit.
The possible closures are part of a radical overhaul proposed by a special administrator in response to nearby South London healthcare NHS trust (SLHT) going into administration after it started losing around £1.3m a week.
But the Labour leader said decisions in the health service should be based on "clinical judgments, not by cost judgments".
He told ITV1's Daybreak: "I hope they will save the A&E in Lewisham because I think it's very important for people there and I think we have seen a huge groundswell of people in Lewisham who are really concerned about what's happening there.
"But I think it's part of a wider problem we have in the health service under this government. I think you've got to take the nurses, the doctors, the patient groups with you, not fight against them, which is what we've seen so far."
The reorganisation proposed by the special administrator Matthew Kershaw to deal with SLHT's collapse is intended to save about £42m from the staff pay budget.
Previous estimates suggested those savings would include cutting 140 medical staff across the trust's three hospitals.
The shadow health secretary, Andy Burnham, also criticised the proposed changes at Lewisham, saying: "If that were to be approved, I believe it would set a dangerous precedent to the NHS when the NHS is taking out A&E capacity on the basis of finance, not on care and quality, and that is a line over which the government must not cross.
"What is being proposed is to solve the financial problems in one trust, the suggestion is they take away the A&E of a successful trust next door. Now that isn't reconfiguration on the premise that we've been doing it for the last however many years, which is there must be a clinical case for change. I've seen no clinical case, looking at the wider impact on A&E across south London.
"There hasn't been an A&E under this pressure where there are already safety concerns. How can you just take out A&E on the back of fairly arbitrary financial calculations?"
Burnham said £6m had already been spent on the administration process, describing it as a "colossal waste of money".
He added that A&E departments are "full to bursting", with more than 47,000 extra patients waiting at least four hours this winter compared with last.
"What we are revealing is an NHS that is going through its worst winter in almost a decade," Burnham said as he published Labour's NHS Check report.
"With A&E in parts of the country really struggling under the strain and where performance has dipped well below the government's reduced target, in places it isn't coping."
The government reduced its A&E target so that 95% of patients must be seen within four hours, but the figures show that only 94.7% are being seen within that period. Some trusts are operating "way below" the target, Burnham said.
Additionally, more than 47,000 patients have waited more than four hours in A&E this winter compared with the last, with more than 100,000 extra patients waiting longer than four hours in A&E since the start of the NHS 2012-13 year, the report shows.
Patients are also being forced to spend more time waiting on trolleys, with an extra 23,000 having to wait longer than four hours compared with 2011-12.
