He continued his involvement with the International Socialists into the early 1970s, attending branch meetings in West London, with his old Napier friend, Blair Peach.
His plays included Midnight in Moscow — which The Press reviewer Alan Scott called "entertaining and thought-provoking" and "one of his best to date" — 2005's Iraq-set Baghdad, Baby, and an adaptation of Nicky Hager's exposé The Hollow Men.
He won awards in New Zealand for teleplay Share the Dream (starring Joel Tobeck), and co-writing the successful big-screen comedy Came a Hot Friday.
Arguably his best-known television work is Welsh-Kiwi rugby tale Old Scores, which Parker co-wrote with ex All Black triallist and occasional soccer player Greg McGee.
The two also co-created the 1980s trucking series Roche, whose cast included John Bach and Andy Anderson, and goldmining drama Gold, a co-production between New Zealand and Canada.
Parker also worked on episodes of police drama Mortimer's Patch, Betty's Bunch, and documentary Just Slightly, A People Apart: The Irish in NZ.
Horrified at the election of National Prime Minister, Robert Muldoon, Parker joined the pro-Soviet Socialist Unity Party of New Zealand and soon became chairman of its Auckland City Branch.