N-Dubz star Dappy has been forced to apologise after showing support for a knife killer in a new music video.
Dappy called for Learco Chindamo, the killer of headteacher Philip Lawrence, to be be freed in a video for his latest song.
The film, for his new single, has the message "Free Leo Chindamo" in the opening credits.
In a statement on his Twitter, he wrote: "Just wanted to say I honestly wasn't aware he did that, I knew his brother from when I was young.
"In no way did I intend to cause any upset and certainly didn't know about his past. My heart goes out to Mr Laurence's family and I know the pain of losing a loved one, sincerely Daps."
Chindamo was released in 2010 after serving 12 years behind bars, but was jailed again just four months later after being arrested over allegations of robbery. He was later cleared.
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, it is understood.
He was originally jailed for life with a minimum of 12 years after stabbing Mr Lawrence outside his school in west London in 1995.
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."
He also tweeted fans telling them: "Hope ur enjoying Tarzan Part 2. Like i told u im just warming up. Its only right 1 of us tells it how it should."
