Justin's performance at the event's Chelmsford, England site last month (Aug16) drew heavy criticism after a number of fans alleged he'd lip-synced parts of his set.
A representative for the 22-year-old singer subsequently denied the allegations saying there was "no miming".
However the Love Me Again musician, 26, has now added his voice to those who felt the pop superstar's performance was unacceptable.
"What he (Justin) did was not cool man," John tells Britain's Daily Star newspaper. "I know how much effort goes into festivals, so I'll say thank you on stage to the crews. Then that guy walked on with his microphone by his knees not even pretending. That's ridiculous!"
Justin did admit that he was not at his best on the V Festival stage, saying during his set he was "hungover" and needed fast food to "soak up all this alcohol in my system".
The singer was pictured leaving London's Tape nightclub at 5am on the morning of his performance. He had been partying with fellow V Festival headliner Rihanna.
Although some fans accused Justin of miming others defended the musician, pointing to a segment of his set which featured him playing stripped down versions of his hits on acoustic guitar as evidence he had sung live.
John caused no such controversy with his performance at the festival, drawing rave reviews for his energetic set delivered despite his recent brain tumour diagnosis.