A nursing home has been told to sort out its act after an inspection found unsafe arrangements for managing medicines.
The Care Quality Commission (CQC) demanded urgent improvements at the Dulwich Care Centre, in Knollys Road, Streatham, to stop elderly residents being put at risk of harm.
The warning notice was issued after an August inspection found some doses had not been given when recorded and some medicines had been given but not recorded.
Matthew Trainer, deputy director of CQC in London, said: "Poor medicines management can have serious consequences for people living in nursing homes.
"The issues identified at the Dulwich Care Centre were in need of immediate action.
"Our inspectors will return in the near future to carry out another inspection.
"If we find that the home is not making the required progress we won’t hesitate to use our legal powers further to protect the people living there."
Geoff Daly, director of T D Bailey Investments Ltd, which owns the care centre, said: "We acknowledge that there were shortcomings in the documentation surrounding the administration of medicines at the time of the CQC visit.
"These issues were immediately addressed by further training for staff and more robust audits put in place.
"A CQC inspector visited again on Wednesday and was impressed by the improvements implemented.
"While we await the formal outcome of her visit, we are confident that all issues have been resolved and, as a result, that the formal notice will be lifted in the coming days."
The council has placed 51 residents at the privately run centre and has been working with the CQC to set out how the centre must improve.
A spokesman said: "We are monitoring the implementation of these improvements closely.
"Along with the CQC, council staff are making regular and unannounced visits to ensure the wellbeing of residents, and all families and carers have been contacted."
During an inspection on August 16 gaps were found in the recording of medicines given to four people.
Inspectors also noticed that an antibiotic was prescribed three times a day for one person but given four times a day for three days.
In addition a 14-day supply of medicine had run out for another person but nurses had recorded that it was given for 16 days.
Their audit found discrepancies in the stocks for 14 medicines compared to records while medicines were not always kept safely and medication trolleys left unlocked.