US actor Harry Shearer - best known for voicing several characters in 'The Simpsons' - has announced he is set to leave the show.

Shearer tweeted to say it is because he wants the freedom to do other work.

Quoting the lawyer of 'The Simpsons' producer James L Brooks, he said the show "will go on, Harry will not be part of it...Of course, I wish him the very best."

Shearer has also thanked fans for their support:

Thanks, Simpsons fans, for your support.

— Harry Shearer (@theharryshearer) May 14, 2015

Shearer (71) has been a part of 'The Simpsons' cast since 1989, voicing such characters as Mr Burns, Waylon Smithers, Ned Flanders, Reverend Lovejoy, Kent Brockman, Dr Hibbert, Lenny Leonard, Principal Skinner and Rainier Wolfcastle.

He is also the recipient of two Cable Ace Awards.

Film audiences will also know Shearer for his work on the mockumentary, 'This is Spinal Tap'.

Spinal Tap, the band, have enjoyed worldwide success performing live and five years ago stole the show at the Live Earth concert in London.

But as one memorable Simpsons character would say, 'boo-urns'.