George, 61, cannot work because of a painful back problem and he said he and his wife Kathy, Bieber's step-grandmother, have received no support from the 'Baby' hitmaker, reported Sun online.
The lack of help comes despite Bieber's grandparents having very limited income and living in difficult conditions. "Justin has just got too big for his britches. He never calls us and now I sometimes think he doesn't care.
He seems to be getting caught up in this lavish lifestyle and has forgotten us," George said. As his grandparents continue to struggle, the 19-year-old pop star recently endured a difficult and controversial UK trip including a confrontation with a photographer and turning up two hours late for a show.
"When I hear about his recent behaviour I just wonder who on earth is looking after him as, believe me, this is not the loving little boy we always knew. It's like we now live on different planets," he added.
And Bieber is apparently able to help his maternal grandmother and her second husband, which upsets George. "For them nothing seems to be too much trouble. He buys them new houses, cars, luxury holidays - anything they want.
But for us - nothing. "I would love a new house as now I cannot even make it upstairs, my back is so bad. But I guess that is not on the cards for us," George said. George said that their situation is becoming 'desperate' and he can't grasp the level of wealth his grandson now enjoys.
"Justin might be worth 70 million pounds but we certainly have never seen a penny of it. It does make me sad, as right now our life is pretty desperate. It's had to imagine the money Justin has, as it's about as far removed from our life as you could get," he said.
Spotted: Virat Kohli, Anushka Sharma and other celebs at Mumbai airport
Photos: Salman Khan's 'special friend' Iulia Vantur at a song launch
Photos: Hrithik Roshan, Anushka Sharma, other celebs dazzle at event
In Pictures: Sex scandals involving Indian politicians
Photos: Abhishek Bachchan and Farah Khan at Boman Irani's birthday bash