A 35-year-old woman was arrested on Thursday after parents complained that their babies became listless after she babysat them.
Mr Tan, who asked that his family members' names not be revealed, told The Straits Times that his 11-month-old daughter is still in hospital after spending eight hours at the nanny's home in Hougang on Christmas night.
The nanny advertised on Facebook and claimed to be a former nurse. She charged them $30.
His wife said that when they dropped their daughter off at the flat, the nanny assured them that she would take good care of the toddler. But when they went to pick their daughter up the next morning at 6am, the usually active child was drowsy and her eyes were half-closed, Mr Tan said.
"She looked drugged, was cranky and couldn't sit straight."
Even after a nap, his daughter still appeared drowsy and could not control her limbs.
The Straits Times understands that at least two police reports were made against the nanny.
Mr Tan said his daughter will be hospitalised until next week.
During the arrest, police took away medicines from the nanny's home, including cough mixture, Shin Min Daily News reported.
Police said investigations are ongoing.
•Additional reporting by Tan Tam Mei