As a result, the government introduced the teaching of Māori in primary and secondary schools as an option.
His efforts, and that of the Māori Language Society, led to the establishment of Māori Language Day, which later extended to Māori Language Week in 1975.
Smith also fought for Homosexual Law Reform in 1986.
He was also senior language adviser at Te Taura Whiri.
Last year Smith told RNZ he was optimistic about the survival of te reo Māori in Aotearoa.
"I'm very optimistic, I'm a cynical optimist though, because change takes a lot of time and I'm talking 45 years when suddenly a lot of New Zealand is coming on board.
"What we're going to see is not only the proliferation of the learning and the teaching of the Māori language, but we're going to see a major increase in tribal or regional dialects which have been put to the side a bit, mainly through the standardisation of our language.
"I was never encouraged to speak Māori when I was growing up in Kahungunu, in Hastings, it's mad I learnt English and French, and then I learnt Russian, all at high school and I didn't learn Māori until I came to Victoria University."