The parliamentary system outlined in the 1956 constitution required disciplined political parties, which did not exist. The Muslim League--the one political party that had appeared capable of developing into a national democratic party--continued to decline in prestige. In West Pakistan, Sindh and the North-West Frontier Province resented the political and economic dominance accorded Punjab and were hostile to the "One Unit Plan" introduced by the Constituent Assembly the year before. The One Unit Plan merged the western provinces of Balochistan, the NorthWest Frontier Province, Punjab, and Sindh into a single administrative unit named West Pakistan, which in the new Legislative Assembly was to have parity with the more populous province of East Pakistan.

In 1956 Suhrawardy formed a coalition cabinet at the center that included the Awami League and the newly formed Republican Party of the West Wing, which had broken off from the Muslim League. Suhrawardy was highly respected in East Pakistan, but he had no measurable political strength in West Pakistan. By taking a strong position in favor of the One Unit Plan, he lost support in Sindh, the North-West Frontier Province, and Balochistan.

Societal violence and ethnic unrest further complicated the growth and functioning of parliamentary government. In West Pakistan, chief minister Khan Sahib was assassinated. In the North-West Frontier Province, Khan Sahib's brother, Khan Abdul Ghaffar Khan, of the National Awami Party, turned his back on national politics and said he would work for the attainment of a separate homeland for the Pakhtuns. And in Balochistan, the khan of Kalat again declared his independence, but the Pakistan Army restored Pakistani control.

On October 7, 1958, President Mirza, with the support of the army, suspended the 1956 constitution, imposed martial law, and canceled the elections scheduled for January 1959. Mirza was also supported by the civil service bureaucracy, which harbored deep suspicions of politicians. Nonetheless, on October 27 Mirza was ousted and sent into lifetime exile in London. General Ayub Khan, the army commander in chief, assumed control of a military government.

Data as of April 1994