Mujib left Muslim League and launched his political carrer in Awami Muslim League, the predecessor of the Awami League, with Suhrawardy and Maulana Bhasani.He was elected Jt. Secretary of its East Pakistan Unit in 1949.
Mujib and Suhrawardy,1949
While Suhrawardy was engaged in forming a larger coalition of East Pakistani and Socialist Parties Mujib tried to organise the grassroots organisation.
In 1951 he began organising protests and rallies in response to the killings of students by police on peaceful picketing for Bengali as their state language.In 1953 he was made the Party's General Secretary and elected to the East Bengal Legislative Assembly on a United front coalition ticket in 1954.Serving Briefly as a Minister for agriculture , he was arrested for organising a protest for dismissing United Front Govt. by the centre.He was elected to the second Cosntituent Assembly of Pakistan and served for 1955to 1958. In a speech delivered in the assembly on the proposed "one unit" plan , Mujib reiterated that the Bengali people's ethnic identity be respected and the matter might be decided in a popular verdict.
In 1956 Mujib entered a second coalition Govt.as minister of Industries, Commerce, labour, anti-corruptionand village aid but he resigned in 1957to work full time for the Party Organisation.
When Gen. Ayub Khan suspended the constitution and imposed martial law in 1958, Mujib was arrested and imprisoned till 1961. After release he started a political underground organisation Swadhin Bangla Biplabi Parishad to oppose the regime of Ayub and to work for more political power for Bengalis and independence of East Pakistan. But again he was arrested in 1962.