A US college football star says he was duped into an online relationship with a woman whose “death” from leukaemia was faked by perpetrators of an elaborate hoax.

The death had been part of a dramatic series of events as young Manti Te’o led his Notre Dame team to the national championship game.

Before a game last year, word spread that Te’o had lost his grandmother and girlfriend within hours of each other.

His inspired play afterwards became a stirring story line. But in a shocking announcement last night, Notre Dame said the girlfriend, Lennay Kekua, never existed.

The goal of the scam was not clear, though Notre Dame said it used an investigative firm to dig into the details after Te’o disclosed them three weeks ago.

The hoax was disclosed hours after Deadspin.com posted a lengthy story, saying it could find no record that Kekua ever existed.

The story suggests a friend of Te’o may have carried out the hoax and that the football player may have been in on it.

“This is incredibly embarrassing to talk about, but over an extended period of time, I developed an emotional relationship with a woman I met online,” Te’o said in a statement.

“We maintained what I thought to be an authentic relationship by communicating frequently online and on the phone, and I grew to care deeply about her.

”However, he stopped short of saying he had ever met her in person or correcting reports that said he had, though he did on numerous occasions talk about how special the relationship was to him.