After standing as a communist at a mock school-election and flirting with distributism at university, Forth developed both conservative and libertarian leanings. Forth was elected as a councillor for the Pilgrims Hatch ward on the Brentwood Urban District Council from 1968 to 1972. He contested the safe Labour seat of Barking at both the February and October 1974 general elections, where on both occasions he was defeated by Labour's Jo Richardson. He was the secretary of Llandeilo Conservative Association from 1975 to 1977, and chairman of the Ross-on-Wye Conservative Political Committee from 1978 to 1979.