CBB's Grant, 56, was the first celebrity to be evicted from the current series and he had previously been seen getting on well with 24-year-old Marnie.
In fact, the pair were shown lying on the bed together during an episode of Celebrity Big Brother's Bit On The Side, before Grant leaned in towards her chest to smell her.
And in the Diary Room, Marnie told Big Brother: "He's a dark horse, I think he fancies me. I feel like we're kind of flirting!"
But speaking on ITV1's This Morning today (9 August), Grant - who was married to TV presenter Anthea Turner - brushed off any suggestion that he and Marnie fancied each other.
He said: "My relationship was pure sport, it was a bit of a laugh and a joke. It wasn't flirtatious, it was a bit of a TV soap moment."
During his interview with presenters Eamonn Holmes and Ruth Langsford, Grant did admit that he often forgot the cameras were on him.
"If I'm honest, when you're in the house, you do actually forget the cameras are there," he added.
And when asked why he was so keen to change public opinion of him, Grant explained: "I'm a human being. Some of the things that have been written about me over the years are toe-curling and I'm a father, I have children and my children read it, as do their friends.
"I wanted a right of reply, rightly or wrongly, and I feel I've got that."
Tonight's CBB will see another housemates shown the door in a live eviction, hosted by Emma Willis. Those facing the boot are Stephen Bear, Lewis Bloor, Saira Khan and Heavy D.
CBB continues at 9pm on Channel 5.