hotpoint tc71 dryer wont start but if you push drum it will go?

hi i have a hotpoint dryer tc71 which a couple of days ago stopped working. the drum will not turn but if i open it up and assist the drum from inside then it will slowly go and then get up to full speed but as soon as it changes direction it stops again it seems like there is not enough power to turn the drum as if the motor was week of something so i was wondering if you could help. could it just be the drum belt that needs replaceing or could it be something more sinister.

regards andy