A breastfeeding support group has rejected a call for a unified declaration from health authorities that sleeping with small babies is dangerous.

A Victorian coroner criticised the inconsistent advice given to parents get about babies sleeping in the same bed.

Coroner John Olle said more uniform advice about the risks of co-sleeping was needed after investigating the deaths of four babies aged between 10 weeks and five months which died of SIDS, or sudden infant death syndrome.

All had been sleeping in a bed next to at least one of their parents when they died, which he labelled "inherently dangerous".

He said in the first six to 12 months of life, babies should sleep on their backs in a cot in the same room as their parents.

However, the Australian Breastfeeding Association's Renee Kam says making a blanket statement that co-sleeping should or should not be done is dangerous.

Ms Kam says parents need all the information on risk factors.

"People who co-sleep with their babies have an increased duration of breastfeeding," she said.

"We also know that breastfeeding reduces the risk of sudden infant death syndrome."

New South Wales Health links to a SIDS site which is against co-sleeping, but its advice for indigenous parents, only says do not share beds when parents have been smoking or have had alcohol.