Armstrong was a member of the New South Wales Legislative Assembly for Lachlan from 19 September 1981 to March 2007. He was Minister for Agriculture and Rural Affairs from 1988 to 1993. From 1993 until 1995, he was Deputy Premier of New South Wales as well as Minister for Ports and Minister for Public Works.[1]
The Coalition government was defeated at the 1995 election and Armstrong stayed on as National Party leader when the Coalition then went into Opposition.
During this term in Opposition, a motion in the Legislative Assembly to gag Armstrong was passed thanks to the casting vote delivered by Labor Speaker John Murray against him and Murray attracted criticism for using his casting vote this way.
Although Armstrong was set to lead the Nationals at the March 1999 state election, he was unexpectedly ousted by his deputy George Souris just two months beforehand. This ousting came a month after Peter Collins was deposed as Liberal leader by Kerry Chikarovski.
Armstrong's seat of Lachlan was abolished shortly before the 2007 state election. This change prompted Armstrong's decision to leave the parliament; he had no particular interest in finding another constituency to represent, and he had already been in the legislature for more than a quarter of a century.
Nevertheless, Armstrong's public life did not end in 2007. Six years later he was appointed the inaugural Chair of Central Tablelands Local Land Services.
The Ian Armstrong Building in Orange was named after Armstrong. It houses the headquarters of NSW Department of Primary Industries and offices of other state government departments.[4][5] The building was officially opened and named in September 2020, a few months before Armstrong's death.