Justin Bieber's grandmother feels sorry for him.

The 19-year-old singer's maternal granny Diane Dale has defended his recent bad behaviour, which includes peeing in a mop bucket while shouting ''F*** Bill Clinton'' [the former President of the United States] and partying at nightclubs in the U.S. despite being two years underage.

She told Canada's CTV: ''It's totally crazy. I feel sorry for Justin all the time, because paparazzi pick on him all the time.

''Anybody else's kids have done the same thing but nobody says anything. He's a 19-year-old boy. And before you criticise him, say, 'What is my 19-year-old boy doing?''

Diane recently insisted that the Canadian singer hasn't changed despite his huge success.

She tweeted: '''Well the kid hasn't changed much' is one of the biggest compliments we have received.''

While Diane thinks that Justin's behaviour is completely normal, his mother Pattie Mallette asked journalists not to ask her about his controversial antics while promoting her new autobiography 'Nowhere But Up: The Story of Justin Bieber's Mom' this week.

But Pattie previously revealed that she thinks Justin will grow up and eventually get his life back on track.

She recently said: ''My son is not a public figure to me, he is my son. I can't predict what's going to be in the headlines.

''Justin has always been someone who has to do things his way. And I have to be able to believe he will do the right thing and he will come out on top.''