One Direction star Harry Styles' sister has urged his fans to "stay sharp, stay suspicious, stay safe" after releasing information about a bogus Twitter account preying on vulnerable girls.

Gemma Styles has discovered a Twitter account under the handle @PrvtHarryStyles, billed as a private page belonging to her brother.

The account was set up to help female fans with mental health issues, but Harry's sister has alerted the 10,000 followers signed up it's a Twitter address her brother has nothing to do with.

"For people asking @PrvtHarryStyles is NOT a real account," she wrote on Thursday night (16Feb17). "Do not send pictures or anything else. Stay sharp, stay suspicious, stay safe."

She added: "Sad that I even have to tweet this but for my own conscience I don’t see an alternative. Young girls don’t need this. For the record none of us have 'private' accounts, what would the point even be? Sadly some people will just believe what they want to believe, but what else can I do?"

The account has since been suspended by Twitter bosses, according to The Sun.

The drama prompted a social media response from Harry's fans, who claimed the person behind the account had been asking young girls for pictures.

One devotee wrote: "Teen girls have been sending that account things & I’ve been horrified that someone is preying on them."

Another added: "That fake Harry account was actually getting money from people. They would buy things on some site and he would get coins for the stuff they bought. So basically this dude got money and nudes from minors."