Mr Horomia had been a particular champion of Maori Women's Welfare League in Wairarapa, Mr Kerehi said, to which his commitment had remained strong even after his term had ended as Minister of Maori Affairs.
"He was someone who, if called upon, would always call straight back and be over here and working out solutions."
Nelson Rangi, Kahungunu ki Wairarapa governance board chairman, said there would likely be numerous mourners travelling from Wairarapa to the tangi, as Mr Horomia had been widely respected in the region.
"He always was a very bright bloke who was tremendously popular with many people here."
Mr Horomia also was well-liked among his political peers and was regarded as the Labour "kaumatua" in Parliament, respected for his widespread links to Maoridom. Mr Horomia was born in Tolaga Bay and was raised in an extended whanau.
He also held roles that included chairing Ngati Porou, the Te Kohanga Reo Trust Training Board and the Hatea Rangi Maori Council, working as a Maori warden and a member of the Youth Advisory Board, the New Zealand Lotteries Board and several Maori organisations.
Mr Horomia represented the East Coast in rugby and remained a keen supporter. He played in the parliamentary rugby team into his 50s.
In his younger days he also participated in many other sports. His interests included gardening, travelling and listening to jazz and blues.
He was of Ngati Kahungunu, Ngati Porou, Ngai Tahu and Te Aitanga Hauiti descent.
Mr Horomia married Gladwyn and they had three sons. Mrs Horomia died of cancer in 1993.