During an appearance on the Private Parts podcast, he read a tribute she'd penned about him, in which she called him her "soulmate".
Sounding tearful, Murs said he was trying to "keep it together".
The message, penned for Murs when he was going on tour, said: "When I met Olly for the first time it felt like I had met my soulmate.
"Not in a weird way, it was just like meeting someone I’d known all my life.
“I’ve never laughed as much as I did in 2011 when we first hosted The Xtra Factor together and that experience will always stay with me forever.”
The Dance With Me Tonight singer became more emotional as he read: “He’s one of the most talented people I’ve ever met in my whole life and he puts 100% into everything he does.
“He keeps the whole team going and for that I forgive him for his dad jokes.”
Murs has often opened up about how much he misses Flack, who was found dead in her London flat on 15 February 2020, at the age of 40.
And on the podcast he said it was still hard and that he thinks about the late presenter every day.
He said: “Knowing obviously the pain she must have been in to take her own life, to hear her say ‘I’ve never laughed as much as I did in 2011’ and that memory of us being together was one of the moments.
“Just little things like that…”
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