[3] He served as Minister of Finance of Sierra Leone in Milton's government after 1962, where he also held positions alternatively in Education, Agriculture, and Natural Resources.
Margai was a founding member of the Sierra Leone National Party, which was formed in 1949 to advocate and aid in the transition to independence for the country.
He was one of a number of leaders (Kwame Nkrumah in Ghana and Milton Obote in Uganda are other examples) who attempted to remove the system of democratic governance enshrined in multi-party democracy as he believed that this would encourage politicians to accentuate the ethnic differences within the state and therefore threaten the viability of Sierra Leone as a country.
The tantrum-prone Prime Minister was nicknamed "Akpata", a Mende word meaning "our wild, fat man".
Margai's opponent Siaka Stevens achieved a small parliamentary majority and he was sworn in as the third Prime Minister of Sierra Leone by Governor-General Sir Henry Lightfoot Boston.
[5] Margai's friend and ally Brigadier David Lansana, who was the Commander of Sierra Leone's Armed Forces at the time, arrested both Stevens and Lightfoot Boston.
[5] In April 1968, a group of noncommissioned officers staged a counter coup in an attempt to restore the democratic process to Sierra Leone.
[5] Eight member of the officers formed the National Reformation Council and elected Brigadier John Bangura to the post of acting Governor-General of Sierra Leone.
[5] Margai warned: "If the Stevens government does not do something to elevate the lives of the have-nots, the poor, they would one day rise to demand from the haves, the rich, their own share of the economy.