Via the Hollywood Reporter:

The singer made his opinions about former friend Madonna known in an interview with Australia's Channel 7 program Sunday Night, declaring that her career was "over."

“She’s such a nightmare. Her career is over, I can tell you that," John said. "Her tour is a disaster and it couldn't happen to a bigger cunt."

Read more, and watch the video interview—Madonna bashing begins around 7:41 mark.