One Direction's Niall Horan and Amy Green

The One Direction star ended his relationship with Amy Green - which began in October - because of his hectic schedule with the band which didn't leave him enough time to do "everything he has to do."

A source told the Sunday Mirror newspaper: "Sadly, it is over between Niall and Amy. He finished it because he didn't have enough time with everything he has to do.

"Understandably she was disappointed because she had been in a relationship before she started seeing Niall and chose him over her boyfriend.

"But there are no real hard feelings and they're still close."

However, an insider has claimed the 20-year-old aspiring actress-and-model threatened to break up with the 'Little Things' hitmaker earlier this month because Niall, 19, was too immature.

The source said: "It was like [his] first relationship, whereas Amy had been in a relationship before. They had a few silly arguments and it was really the beginning of the end."

While Niall is said to have never felt happier, his now ex-girlfriend has refused to comment on the split, although a close friend has said she hopes they'll stay friends.

Speaking outside her family's north London home, Amy said: "I don't know what I should or shouldn't say. Sorry."