The Housing Ombudsman launched an investigation after the death of Awaab Ishak, who lived in a mouldy flat owned by Rochdale Boroughwide Housing (RBH).
Until the two-year-old boy's inquest, the company had struggled to "learn from its mistakes", the report said.
RBH's interim chief executive Yvonne Arrowsmith has apologised.
"We accept their findings," she said. "Sadly for me there were things that weren't surprising, there were things that we've found over the last few months that need to be addressed and really I'd just like to start by saying sorry." เว็บพนันบาคาร่า