Parliamentary form of government is based on a fusion of legislative and executive powers; on the other hand, presidential form of government is based on a separation of powers, where all the three organs of the government are separate and independent of each other.
In a parliamentary form of government there is the presence of a nominal head and a real head. Though the President, who is the head of state, is vested with vast constitutional authority, in reality all these powers are exercised by the Prime Minister and his council of ministers. In a parliamentary form of government the executive is collectively as well as individually responsible to the legislature, while in a presidential form of government the executive is not responsible to the legislature.
In a parliamentary form of government the Prime Minister suggests the names of ministers to the President, who formally appoints them. The Ministers have to be members of either house. If they are not, they have to get elected within a period of six months. In a presidential form, the ministers are not members of the legislature. The President’s cabinet comprises of members who are experts. They are accountable not to the legislature but to the President.
In a parliamentary form of government ministers initiate important bills in the parliament and get them approved, while in a presidential form, the members of the Presidential cabinet cannot initiate any bills in the legislature.
In a parliamentary form of government the tenure of the cabinet depends on the support it commands in the legislature. While in a Presidential form the President enjoys a fixed tenure.