Shadow Health Secretary Andy Burnham said plans to close the A&E department at Lewisham Hospital were "taking the NHS into new ground" and were "dangerous" given the pressure on A&E services.
"When we were in Government we did close some A&Es because sometimes it makes sense to do that, you can save more lives by centralising services on one particular site, every locality cannot necessarily sustain an A&E," he said.
"However what is different about Lewisham is that this A&E is being closed purely on cost grounds.
"To solve financial problems in one trust, the Government are saying they are going to take away the successful A&E department of another. That is taking the NHS into completely new ground.
"I think it is dangerous to do that, given the pressure that we seeing on A&E in London and right across the country."
More top news
Police in Southwark are appealing to the public for help in finding a teenage girl missing from Bermondsey.
Over 40,000 people picked up their packs to take part in the annual marathon in the capital.
The boyfriend of reality TV star Ferne McCann has been arrested on suspicion of attempted murder following an alleged nightclub acid attack.