They're enjoying a rapid rise to fame in America but One Direction won't be enjoying their success in a traditional boy band fashion - they've been ordered off nookie by record company bosses.

The four single lads in the band - Niall Horan, Harry Styles, Zayn Malik and Louis Tomlinson - have been ordered: no girlfriends and no sex.

US music executives are said to be desperate to protect the band's clean-cut image as they storm the Stateside charts and have laid down the law to ensure they appeal to the teen market.

Newly single Harry is apparently furious at the strict rules - the 18-year-old is ready to date following his recent split from The Xtra Factor host Caroline Flack.

A source told The Sun: "He's come out of a relationship and wants to enjoy his freedom. But he's having to behave himself and keep the women at arm's length. They are all young lads and they have urges like anyone else their age. And the worst thing is the American girls are literally throwing themselves at them so there is so much temptation in their way."

Fellow band member Niall is also seething as he struggles to steer clear of fans who are falling for his Irish accent in their droves.

A source close to Niall said: "He's raging about it - all the lads are. Four of them are single and they've been told to stay that way as it appeals to their American teen fans. Niall is fighting off the women with his Irish accent and good looks so he's having to live like a monk."

However, it seems Niall and his pals are succeeding at sticking to the harsh new guidelines.

On the group's American fans, he recently told Heat magazine: "We've had a few flashers - but we're not encouraging it, or deterring it!"

Speaking to The Sun, the source added: "Niall and the boys are being kept on a really tight leash and it is tough for them. But they are so determined to make it work in the States they'll do whatever they are told.

"Quite simply a sex scandal over there would be the end of the band."

ONE DIRECTION'S FAMILY ALBUM

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• One Direction's Family Album

  Which Directioner is this? (Pic: Rex)

• One Direction's Family Album

  Which Directioner is this? (Pic: Rex)

• One Direction's Family Album

  It's Harry! (Pic: WENN)

• One Direction's Family Album

  Which Directioner is this? (Pic: Rex)

• One Direction's Family Album

  Which Directioner is this? (Pic: Rex)

• One Direction's Family Album

  It's Liam! (Pic: WENN)

• One Direction's Family Album

  Which Directioner is this? (Pic: Rex)

• One Direction's Family Album

  Which Directioner is this? (Pic: Rex)

• One Direction's Family Album

  It's Louis! (Pic: WENN)

• One Direction's Family Album

  Which Directioner is this? (Pic: Rex)

• One Direction's Family Album

  Which Directioner is this? (Pic: Rex)

• One Direction's Family Album

  It's Niall! (Pic: WENN)

• One Direction's Family Album

  Which Directioner is this? (Pic: Rex)

• One Direction's Family Album

  Which Directioner is this? (Pic: Rex)

• One Direction's Family Album

  It's Zayn! (Pic: WENN)