Zardari made the remarks while interacting with a delegation of the South Asian Free Media Association at his private residence in Lahore last night.
The PPP, which led the government at the centre for the past five years, was routed in the May 11 polls by the PML-N.
Asked what he would have done differently about the 2013 polls, Zardari replied he should have resigned from the presidency to steer the electioneering.
Zardari stopped participating in political activities earlier this year because of pressure from the Lahore High court, which ruled that the President was expected to be apolitical and impartial.
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He was unable to campaign for the PPP, and his son, Bilawal Bhutto-Zardari, was never seen in public during the electioneering.
The PPP could not conduct a proper campaign in Punjab province because of threats from the Taliban and the judiciary too was against the party, Zardari said.
"The party couldn't fight on multiple fronts simultaneously," he said.
Former premier Raja Pervez Ashraf was fighting court cases and other top leaders were detached from the campaign for one reason or the other, he added.
Zardari also blamed the energy crisis for the PPP's poor performance.
"The PPP government could not handle the electricity crisis and this caused the party's defeat," he said.
Expressing doubts about the transparency of the polls, Zardari said returning officers had played an "important role" in the process. He claimed at least 45 seats were "snatched" from the PPP in Punjab.
Zardari dismissed reports that he would step down in the aftermath of the PPP's defeat, saying he intended to complete his constitutional term.
He is set to complete his five-year term in September.