Niall Horan has signed a huge record deal with Capitol US.

A source told The Sun: "Simon has made no secret of his expectations for Niall to stay loyal to him and has been desperately trying to keep him as a solo act with plans to turn him into a Justin Bieber style artist.

"They've worked together closely since day one and have always had a strong relationship, but Universal offered a lot of money.

"Simon's likely to be so frustrated Niall has gone to a rival."

Simon - who guided Niall and his One Direction bandmates to fame after discovering them on the UK 'X Factor' - recently showered praise on the 22-year-old singer and hinted that a big announcement was coming.

He said: "I think they're all gonna do great. Niall is the most loyal.

We are expecting to announce something soon with him. I've always known he's loyal."

Niall's defection is a new blow for Simon after Liam Payne chose to sign his own solo deal with Capitol UK rather than Sony, where One Direction have been with imprint Syco for the past six years.

He said: "I worked with these guys for six years, so I always hoped they would all stay within what I call the Sony family, but I think only one won't."

Simon added that he "always knew" the group - which also comprises Harry Styles and Louis Tomlinson - would want to try to forge careers outside of One Direction and he hoped "that everyone would do it with us, but one flew out of the nest".