The Government was accused of "breaking up" the NHS after announcing a downgrading of accident and emergency and maternity services to deal with huge financial losses at a Trust which went into administration.
The changes at Lewisham Hospital in south-east London are part of a wider shake-up of services in the capital after the financial collapse of neighbouring South London Healthcare NHS Trust (SLHT).
Health Secretary Jeremy Hunt told MPs he had rejected proposals to close the A&E unit at Lewisham, where thousands of people marched at the weekend as part of a campaign to keep it open.
Lewisham Hospital has been hit by the knock-on effects of the financial difficulties of SLHT, which Mr Hunt said would now be dissolved after losses of more than £1 million a week.
Shadow health secretary Andy Burnham said the Government's "mismanagement" of the NHS had got worse, adding that the decision to downgrade services set a "dangerous precedent" for other hospitals.
Rehana Azam, national officer of the GMB union, said: "This Government is now presiding over the downfall, break up and privatisation of the NHS.
"The basic principles of NHS provided free at the point of use and delivery has been tarnished as Secretary of State Jeremy Hunt takes on recommendations to shut down services.
"As people will have to travel further to access services, particularly urgent care in built up areas with congested roads, lives will be put at risk."
The GMB called on MPs to reject today's decision.
Geoff Martin, chairman of campaign group London Health Emergency, said: "The Government have today endorsed brutal cuts to front line hospital services in south London which will have a knock-on effect for hundreds of thousands of people seeking emergency and maternity care.
"The minister has also given the green light to a wave of similar cash-led A&E and maternity closures and downgrades across London which will devastate services throughout the capital and spark an unprecedented campaign of public resistance."
The proposed closure of units at Lewisham Hospital is part of a radical plan to rescue a neighbouring NHS trust from bankruptcy.