Correcting Alison’s error, he added: “Of course, Joan passed away, tragically, seven years ago and it has since been owned by someone else.
“But the late actress is selling this home for $38million or £27million, it has 11 rooms.”
One fan tweeted in response to the mishap: “Alison obviously blissfully unaware that Joan Rivers is actually dead #ThisMorning.”
Another added: “Classic Alison talking about Joan Rivers having a NY penthouse, not realising she died seven years ago! #ThisMorning.”
Alison and Dermot host on Fridays after it was revealed that veteran stars Eamonn Holmes and his wife Ruth Langsford were to front only the half-term episodes of This Morning.
The pair were announced as the new hosts back in January.