Michael Jackson's new single 'This Is It' was actually written more than two decades ago, it has emerged.

Jackson's estate was forced to make the acknowledgement after songwriter Paul Anka revealed he had written the track with the singer in 1983.

The pair penned the track – originally called 'I Never Heard' – for a duets album Anka was recording, and were also credited as co-authors on an early 1990s version by the singer Sa-Fire.

However, 'This Is It' was not initially credited to Anka when it was given its world premiere on Monday.

After threatening legal action, Anka has now been given credit for the song and will receive 50% of the track's profits.

"They did the right thing," Anka told the Press Association.

"I don't think that anybody tried to do the wrong thing. It was an honest mistake."

A statement from the Jackson estate said: "The song was picked because the lyrics were appropriate because of the name Michael gave his tour.

"We are thrilled to present this song in Michael's voice for the first time and that Michael's fans have responded in unprecedented numbers."

'This Is It' is taken from the soundtrack to the forthcoming Michael Jackson movie of the same name.

The movie shows footage of the late singer, who died in June, preparing for his ill-fated comeback gigs in London.

(by Jason Gregory)