Postgate's partner, Naomi Linnell, said the artist and puppeteer died Monday at a nursing home in Broadstairs, 75 miles (120 kilometers) east of London.
Both surreal and warmhearted, Postgate's productions were a staple of British children's television for three decades, beginning in the 1950s. They included musical Welsh locomotive Ivor the Engine, Norse prince Noggin the Nog and The Clangers, a family of mouselike pink knitted aliens who spoke in whistles.
His best-loved creation was Bagpuss, a pink "saggy old cloth cat" who appeared in a 1970s series and has topped several polls of Britain's favorite children's shows.
Postgate - the grandson of British Labour politician George Lansbury and cousin of actress Angela Lansbury - was born in London in 1925. During World War II he declared himself a conscientious objector and was jailed, later serving as a Red Cross stretcher-bearer in Germany. He remained politically active throughout his life, opposing nuclear weapons and the Iraq war.
Postgate attended drama school after the war, then moved into animation with the black-and-white series "Alexander the Mouse."
In the late 1950s, Postgate established the Smallfilms production company with fellow artist Peter Firmin, devising and writing scripts, creating puppets and artworks, and filming their shows in stop-motion animation. Postgate provided the voices and narration.
Postgate is survived by Linnell and several children from his marriage to the late Prudence Myers.