The star - real name Ben Ballance-Drew - has teamed up with the music legend to record a new version of his hit track Hard Times to raise money for aid organisations in Pakistan and Japan.
Plan B was worried the collaboration would damage his "underground" reputation, but he was willing to take the risk for such a good cause.
He says, "I said to my friends all it needs is Ronan Keating's voice and it's cheese. It's proper on the edge - but I'm happy that it's just on the edge... love my hip-hop, my underground hip-hop and I want to carry on doing that. And releasing a charity record was a bit of a risk for me, doing something so high profile, it risks me crossing that line where I can never go back to doing the underground.
"But there's a lot of people dead and a lot of people injured and suffering over there and I am in this position that I can change something or that I can contribute to making somebody's life better."