The One Direction hunk admitted he still speaks to his former lover - who he split from in January - regularly on the phone but things don't go so well when they meet face-to-face.
He said: "Caroline and I are good friends and we are still in touch.
"Every time we are in the same place we seem to argue, but we get along fine."
Harry has dated a string of older women including 32-year-old Caroline, but insists they aren't the only females he is interested in as he is a natural flirt.
He is quoted by the Daily Star on Sunday newspaper as saying: "I'm 18, I don't love older women, I just love women. Sometimes I flirt without meaning to.
"Perhaps it's just how I was meant to be. I've got a good seduction routine which I execute very well."
Meanwhile, Harry has been accused of ruining a marriage.
It was revealed earlier this year that the 'One Thing' singer had slept with married DJ Lucy Horobin and now her estranged spouse Oliver Pope - who is due to file for divorce this week - has admitted he entirely blames the young pop star.
He told the Sunday Mirror newspaper: "I know how stupid it sounds but I blame Harry 100 per cent for this.
"OK, so Lucy may have technically split from me days before he first slept with her but that came after weeks of flirtatious text messages.
"We were still living together in the same house. At that point, in the same bed.
"She was wearing a wedding ring the first time they met.
"I don't think it matters to him whether the woman he wants is married or not."