In the Legislative Assembly Election of West Bengal in 1951/52, he contested in the Bangaon constituency as an independent candidate against Jibon Ratan Dhar of the Indian National Congress and Ajit Kumar Ganguly of the Communist Party of India.

[1][16] In 1953, due to his continued opposition to the ruling party, Congress, the Indian government accused him of treason and issued him a 24-hour ultimatum to leave the country.

[21] Many of Mosharraf's political compatriots, including Mashiur Rahman and Raushan Ali of Jessore, joined the pro-PDM faction of the Awami League that opposed the Six-point.

Advocate Mosharraf Hossain made a statement in February demanding the release of information regarding the physical condition and location of Sheikh Mujibur Rahman.

An avid political supporter of both the Six-point movement and the 1969 East Pakistan mass uprising,[1][9] Advocate Mosharraf won in the 1970 Pakistani provincial election from Jessore.

[4][27][25] On 18 March 1971, in a joint press statement, Mosharraf Hossain, along with Mashiur Rahman and Raushan Ali, alleged that the local military was trying to create panic among the people and demanded punishment for those involved.

[4] Witness reports from Jessore published in Indian sources mention that the Pakistan army tried fanatically to apprehend Mosharraf Hossain.

[1][5][29] Though he evaded capture during Operation Searchlight,[5] his house in Jessore city was raided on 25 March and later seized by the Pakistan army to be used as a camp.

[7][8] The Provisional Government of Bangladesh appointed him as the head of the Bangaon regugee camp, where food and shelter were provided to incoming refugees from the east.

[22][37] In 1972, a division within the student wing of the Awami League resulted in Mosharraf's elder daughter, Sathi, aligning with Serajul Alam Khan's faction, which espoused the philosophy of Scientific Socialism and opposed Mujibism.

Furthermore, he characterized the Awami League's post-liberation politics as more menacing in terms of deceit and betrayal than that of conspirators like Ayub Khan and Abdul Monem.

[10][12][6][45] Mosharraf Hossain went on to participate in the 1973 Bangladeshi general election as a JSD candidate in the (now defunct) Jessore 9 constituency but lost to Raushan Ali of Awami League.

[49] Following the election, Mosharraf's personal safety became precarious amid an increasingly violent political struggle between Awami League and JSD, plus other left-wing insurgents.