One Direction fans have been sending hate mail to the US band currently suing them for "stealing" their name.

The members of US band One Direction claim that they have been faced with vicious death threats from fans of the British boy band over the copyright breach lawsuit against the former X Factor stars.

According to the California five-piece, they have been inundated with messages from many followers of the What Makes You Beautiful hitmakers.

Sean O'Leary, 18, the US band's frontman and the son of the bands manager Dan told the Sun: "There has been so much hate mail, like people threatening to cut our b***s off.

"The one that stands out for me is a girl saying she wanted to kill my father."

Lawyers for the Californian One Direction filed a copyright infringement claim in California, seeking three times the profits earned by the UK based band and $1 million compensation because they insist they own the rights to the name in America.

They are also seeking an injunction to prevent the British One Direction from using the name in promotional materials.

The low-profile Californian band, who claim that they formed in 2009 - a year before the X Factor boys were discovered on the talent show - say they are entitled to a share of the profits made by their rivals, as well as compensatory damages in excess of $1m.

The lawsuit also claims that the UK group's record companies SyCo and Sony entertainment were aware of the fact the two bands had the same name as early as 2011 but chose to still use the name.