He said: "I'm definitely single. I'd like a girlfriend. All these things in the papers about me saying I'd rather sleep than find a girl is ridiculous. I was just explaining that on my time off I like to chill.
"I'm not actually looking but if the right person came along, definitely."
Niall admits he has gone out with Demi a couple of times but says there's nothing going on between them and are just friends.
He told Now magazine: "What actually happened was that I always used to say in my interviews that I liked her and she also said that she liked me. We got in contact through twitter and we just started chatting and became friends. Demi's one of the nicest girls I know. She's super-cool. She always texts me to see how I am. Nothing ever really happened.
"When I've been in LA and had a few hours to myself, I've seen her a couple of times. We did go for a bit of dinner after the MTV Video Music Awards."