The 64-year-old bassist - who formed the iconic punk band with Johnny Rotten, Steve Jones and Paul Cook - left in 1977 and was replaced by Sid Vicious before the release of their one and only album 'Never Mind the B*******, Here's the Sex Pistols'.
Appearing on the 'Rockonteurs with Gary Kemp and Guy Pratt' podcast, he said: "I think we would never have done 10 albums...
"It was never gonna happen, but we could have made another two or three albums I think."
Opening up on his departure, Glen has discussed his issues with the band's manager Malcolm McLaren, and suggested he never realised the musicians were actually talented.
He added: "I would say this now, but I could see that coming, that was the way it was going, to be like a punk rock Bay City Rollers kind of thing...
"I would say this, but I don't think Malcolm ever understood that we were any good.
"He really thought we was rubbish and he thought he was the bloke who was selling London Bridge - but we could play.
"I wanted to be in a band to play music, I like that side of it."
WHen it came time for his departure, he didn't feel like the other members were giving him support, and he didn't have "an equal say".
He said: "It was coming to a head. I didn't like the way it was going, it was no longer a band where everybody had an equal say.
"I felt I wasn't being backed up and they was being daft... I walked.
"My position became untenable, but if I'd been backed up by Steve and Paul a bit more it wouldn't have been, but they didn't, they didn't see that."
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