When rumours of romance between the couple arose in 2007 Minogue admitted flirting with the music mogul but was clear in her denial of a fling.
"I don't fancy him and I don't have a type I go for, but I like a man who makes me laugh," the Sunday Mirror quoted Minogue as saying.
Cowell, who also denied rumours of an affair at the time, said he hadn't wanted a relationship with Minogue, having just split from his long-term girlfriend.
"They are said to have spent several nights together, but the relationship petered out after a while," an unnamed source told the Mirror.
Minogue later started dating Smith, a former British rugby league player turned model, with whom she has a son.
Meanwhile, Cowell turned his interest to another X Factor judge and singer, Cheryl Cole, but he gives no further details of a relationship with her.
Minogue still works for Cowell on Australia's Got Talent.
She and Smith confirmed their split with messages on Twitter.
"It brings me great sadness to tell you that Kris and I have separated," she wrote.
"We still care for each other and ask for privacy at this difficult time, in particular for our son Ethan who remains our number one priority."
- AAP