Del Graff made the suggestion Tuesday in a report into the death of an unnamed six-week-old girl in 2013.
Her foster parents moved her from a crib into their bed in the middle of the night and she was found unresponsive the next morning.
An autopsy could not determine a cause of death and police ruled there was no crime.
Graff said the province provides a two-day training course for foster parents that includes a section on safe sleeping practices, along with the statement "do not share the bed."
The course was not mandatory but, starting this fall, a new version of it will be.
Graff said that's still not enough.
"Foster parents are taking on the responsibility of providing care to someone else’s child and the decision about bed-sharing should not be the foster parents,'" he wrote.
His report outlines different expert opinions on bed-sharing, including one from the Public Health Agency of Canada that identifies it as a risk factor for suffocation and undetermined death in infants, such as sudden infant death syndrome, or SIDS.
"There are conflicting theories about what is best for babies," said Graff. "Some argue that 'attachment parenting,' which includes bed-sharing, is best, while public health agencies and medical professionals recommend that babies should sleep in a crib.
"But at the end of the day, when children are in the care of the Ministry of Human Services, everything that can be done to make them safe needs to be done."
Human Services Minister Manmeet Bhullar said in a statement that the death of the little girl is a tragedy.
He said his department's policy on bed-sharing will be clarified, but he did not give details.
"While we recognize co-sleeping can be an important cultural aspect, each child in care must have a separate bed or crib as a permanent sleeping arrangement," Bhullar said. "We do not recommend bed-sharing due to a number of associated risks including falls or suffocations."