An assault charge against Justin Bieber has been dropped.

The 20-year-old singer was alleged to have assaulted a limousine driver in the early hours of December 30 but the charge was withdrawn in a Toronto court Monday after prosecutors said there was "no reasonable prospect of conviction".

The Never Say Never hitmaker was said to be "relieved" following the verdict and is ready to get on with his "busy career".

Police alleged Justin was one of six people who got in the limo in the early hours of December 30, and there was an altercation while on the way to a hotel where one passenger hit the driver in the back of the head a number of times before running away.

Justin's lawyer Brian Greenspan had always insisted he was innocent and is said to have contacted the pop star last week to say he expected the charges to be dropped.