Michael Jackson's sound engineer says that he has unearthed 20 new unfinished songs by the late singer - but that he can't let anyone hear them.

Michael Durham Prince, who worked with Jackson from 1995 until he died, told French newspaper Le Parisien: "I have on my computer 20 unreleased (songs) by Michael, all of them unfinished".

He said that he songs had no vocals on the choruses, so if they are eventually released, "someone would have to be found" to finish them as a "duet".

The Jackson estate signed a reported $200 million deal with Sony not long after his death, which allows them the rights to release up to seven albums of new or remixed Michael Jackson material. They've already released two, but a spokesperson for Sony told AFP that they had nothing currently in the works.

In the interview, Prince said that he believed there would be more albums at some point in the future, "but for the moment, we are thinking more about bringing out new songs every six months".