Haami Tokouru Rātana, usually known as Toko, was born at Parewanui, on the west bank of the Rangitīkei River, on 21 July 1894. He was the eldest of seven children of Tahupōtiki Wiremu Rātana and his first wife, Te Urumanaao Ngāpaki (also known as Ngāuta Urumanao Baker). His principal descent group on his father's side was Ngāti Apa, but he was also connected to the Wanganui peoples, Ngāti Ruanui, Ngāti Raukawa, Taranaki and Te Āti Awa; his connections to Ngā Rauru and Ngāti Hine were through his mother. He was sent to school at Whangaehu and was fully bilingual.
Toko Rātana enlisted in 1915 and served for four years in the New Zealand Pioneer Battalion at Gallipoli and in France. He was badly gassed and suffered ill health for the rest of his life.
He had probably not returned from the war when in November 1918 his father commenced the religious revival that developed into the Rātana church and political movement. On his return Toko seems to have joined in the movement without reservation. Pressure on Tahupōtiki to use his influence in the political arena grew from 1920; in 1922 he was asked to stand himself or nominate candidates in the Māori seats, but he declined. Toko stood for Western Māori, and newspapers began to dub him a Rātana candidate, but his official stance was independent. He gained a solid 3,037 votes, 798 behind Māui Pōmare.
These results showed the growing support for his comparatively radical position: the Rātana movement was committed to a Māori national identity, self-determination and the redress of grievances through the Treaty of Waitangi. The Māori establishment, on the other hand, was committed to working in co-operation with Pākehā governments and within the strait-jacket, as Toko and the Rātana movement saw it, of traditional tribal leadership.
On 7 April 1924, at Rātana pā, Toko married Rīpeka Uruteangina of Ngāti Apa; she was connected to peoples of the Wanganui River. They accompanied the Māngai (as his father was now called) on his pilgrimage to Britain, France, Japan and other countries in 1924–25. In the month of their departure Tahupōtiki’s officers were re-establishing the Rātana federation. Toko was appointed to its executive council and was secretary of its financial board, though temporary substitutes were appointed while he was travelling. A second trip was made in 1925 to America. With these travels and the work involved in firmly establishing the Rātana movement, there was little time spare to contest the 1925 elections. But in June 1928 Toko's father turned to politics, announcing that, as the embodiment of the Rātana movement, he was dividing his body into four koata (quarters), one each for Eastern, Northern, Southern and Western Māori. Toko Rātana was the appointee for Western Māori.
In 1928, again competing against Pōmare, Toko, although unsuccessful, achieved 3,075 votes. Following Pōmare's death in 1930, Toko contested the by-election but came second to Te Tāite Te Tomo of the Reform Party, who stood as Pōmare's preferred successor.
In 1931 Tahupōtiki Rātana abandoned his politically 'neutral' stance, openly demanding that Rātana followers vote for his koata. Toko was again to be the candidate for Western Māori. Prior to the election Rātana and his koata visited Wellington to attempt to negotiate a political deal with Harry Holland, leader of the New Zealand Labour Party. Toko, as spokesman, laid a document outlining Rātana policy before Holland. After the discussions he announced that the Rātana candidates would be Labour associates, but would stand as independents. In the event Toko again lost to Te Tomo. The voting had been made more complex by the participation of four independents, two of whom, Rima Wakarua and Pēpene Eketone, were followers of Rātana.
As long as there were no Rātana MPs Toko Rātana was clearly accorded respect as the leader of the koata, but when Eruera Tirikātene was elected for Southern Māori in a 1932 by-election he became known as the principal koata. Toko spent time with Tirikātene in Wellington, acting as one of his aides. After Toko's own election in 1935 with a bare 38-vote majority, there was little change; Toko, a gentle and genuinely humble man, suffering from bouts of illness and with no pretensions to oratory, did not attempt to compete with Tirikātene and was happy to accept his leadership.
Toko Rātana gave his maiden speech in the House of Representatives on 21 October 1937, immediately honouring his pledge to his father by bringing up the subjects of major land grievances and the Treaty of Waitangi. He spoke only four more times in the House; twice in 1937 and twice in 1939. After he had been confirmed as his father's successor as leader of the Rātana church he seems to have regarded it as inappropriate.
After the death of his younger brother, Ārepa, Toko Rātana was given the name Te Ārepa in addition to his own. Within the spiritual side of the Rātana movement, he was by now the clear successor to his father, taking over the chairmanship of most of the important committees as the Māngai weakened. Tahupōtiki Rātana died on 18 September 1939, and Toko was confirmed as his successor, taking the title Kaiārahi (leader). He was harried by those who wanted changes to the movement's political and religious policies; without his mother's support he might not have succeeded in keeping Rātana's supporters faithfully following the wishes of the Māngai. Te Urumanaao died on 26 April 1940, after which the burden on Toko increased.
During the war, although often ill (he spent months in Pātea hospital in 1941), Toko Rātana did what he could to support the war effort. He was opposed to conscription, but keen for a home guard to be manned by Māori; he regarded it as natural, and also said it accorded with the Māngai's wishes for Māori to defend their own land. He made strong representations to Prime Minister Peter Fraser when Apirana Ngata attempted to curtail the contact of Wanganui and Taranaki representatives on the Māori War Effort Organisation with Fraser, the minister in charge.
Ripeka Rātana died in 1934, and on 1 December 1935 Toko married Rangimārie Nēpia; they had a son, who died aged seven, and a daughter. After Rangimārie's death in 1938 he married Mei (Maisie) Heemi at Rātana pā on 10 December 1939, with whom he had several children.
In 1943 Toko was returned for Western Māori with a majority of 3,309 votes. This was the first year in which all four Māori seats were held by Rātana members. From 18 to 20 October 1944, as head of the Rātana church, he took part in a Māori summit in Wellington to which other church leaders had been invited; together they made a public declaration of their support for the war effort. The purpose of the conference was to plan the future direction of the Māori War Effort Organisation and the continuance of Māori control over Māori affairs.
This was Toko Rātana's last significant act. He had been ill for months, and each issue of Te Whetū Mārama carried a bulletin on his health. He died at Rātana pā, aged only 50, on 30 October 1944, survived by his third wife and several children. He was succeeded as president of the Rātana church and also as MP for Western Māori by his younger brother, Matiu.