N-Dubz star Dappy has apologised after the video for his latest song caused controversy.
The music video for his new single Tarzan 2, features a call for the killer of head teacher Philip Lawrence to be freed.
The message "Free Leo Chindamo" is clear the opening credits.
It is understood that Chindamo was jailed last year after breaching the terms of his licence by meeting a gang member, breaking a curfew and failing a breath test.
He was originally jailed for life with a minimum of 12 years after stabbing Mr Lawrence outside his school in west London.
Dappy admitted he "honestly wasn't aware" of the high-profile crime which shocked the nation in December 1995.
Adding: "I knew his brother from when I was young. In no way did I intend to cause upset and certainly didn't know about his past. My heart goes out to Mr Lawrence's family. I know too well the pain of losing a loved one."
The video, which has had more than 225,000 views on YouTube since it was uploaded on July 3, also sees the rapper take aim at X Factor supremo Simon Cowell and some of the show's stars including Joe McElderry and Alexandra Burke.
It features people in Cowell masks and at one point, Dappy raps: "Where are they all now? They're bankrupt. Joe McElderry oh a stand-up, Alexandra pull your socks up."