Farhatullah Babar made the request in a letter to retired Justice Fakhruddin G. Ebrahim, chairman of the country's election commission, which will oversee the country's general elections May 11.
The elections will bring about the first democratic transfer of power since Pakistan became independent in 1947. The country has been intermittently ruled by the powerful military for decades since then.
The civilian coalition government of Zardari was the first to complete its full five-year term last March, paving the way for elections.
"I wish to bring to your attention the vilification campaign set in motion by the leadership of some political parties, particularly the PML-N, against the person of President Asif Ali Zardari and its adverse impact on free and fair elections and the need to urgently redress the issue," the Dawn newspaper reported Babar said in his letter.
The PML-N is a wing of the Pakistan Muslim League led by former Prime Minister Nawab Sharif.
Babar said Zardari is the head of the state, representing the unity of the republic, the report said. He said a Pakistani high court recently restrained the president from indulging in political activities and that Zardari had disassociated himself from political affairs of his Pakistan Peoples' Party.
Babar said while the PML-N has been making accusations against Zardari, the president cannot react, in deference to court directives.