He made the proposal in a speech before the Kusog Mindanao forum in Davao City.
Pimentel said a prime minister, who is head of government in the parliamentary system, can be removed from office for serious wrongdoing by a mere withdrawal of confidence by a majority of parliament.
He said this mechanism of no-confidence vote to unseat the prime minister is built into the parliamentary system where the executive and legislative powers are fused together.
"If we have a parliamentary system, the process of booting out the erring head of government is very responsive to public opinion and it is faster to resolve the case," Pimentel said.
There would then be no need, he said, for government detractors to mount protest rallies or civil disobedience campaigns to force the resignation of the government head, which merely creates political instability.
In a parliamentary system of government, Pimentel explained that the erring head of government may be forced out of office without need of proving his/her culpability as required in a presidential system.
He said there is no inconsistency between the shift to a parliamentary system and his earlier proposal to adopt a federal form of government.
"In fact, the twin proposals of a parliamentary system and federalism complement each other," he said.
Pimentel explained that the parliamentary system, as distinguished from the existing presidential system, essentially involves the merger of executive and legislative powers.
On the other hand, he said a shift to federalism pertains to the division of powers between the central government and the component states.
Pimentel cited Germany, Australia and Malaysia as among the countries with a parliamentary-federal setup. — Perseus Echeminada