Smith was the original bassist of the band, playing in the debut concert in the Bolton Institute of Technology, where the main founders of the band, guitarist Pete Shelley and vocalist Howard Devoto, were students, on 1 April 1976.
He rejoined the band after Devoto left and Shelley took the lead vocalist role, around March 1977, when the band played gigs again. The band recorded and released some material with him, such as The Roxy London WC2 (June 1977), a various artists compilation album of bands who played live at The Roxy; and the first Joy Division's live recording Short Circuit; he also took part in the first Peel sessions and recorded the "Orgasm Addict" single. Around October 1977, he was expelled from the band, due to his alcoholism.
He moved to New York City and by 1980, he joined Dirty Looks.
During the late 1980s, Smith played bass guitar for the Manchester based band, Temper Temper, fronted by David Aldred. Smith played bass on their debut album, History of England.
Since then, little of his whereabouts are known. In 1988, he sent a condolence card to Pete Shelley's mother, Margaret, on the death of Pete's father John, whom Garth thought to be a great man. As of 2014, he supports Tyldesley Rugby Union Club. Garth currently plays in a Tyldesley band, Young Once with Tony and Pete. He is also a member of the Tyldesley 'Supergroup' Moondogs, comprising Mocko – the lead singer with Glamorize – , Tony Wragg – the main voice with Young Once – and Chris Ratcliffe of The Covertones, musician without portfolio on sax, keyboards, guitar and vocals. Garth plays double bass with this 1950s good time band.