Answer:
A parliamentary system of government is a type of government whereby the executive arm of government is responsible/accountable to the parliament.
Therefore, if a parliamentary government does not have a parliament, no laws can be passed, the citizens would have no representation, no government would be formed or chosen and there would exist little or no checks and balances.
The president needs the approval of the parliament before any law is passed, each geo-political zone has a representative in parliament, among other functions and if there is no parliament, there would be a big problem.