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Although Jonathan conceded defeat in the presidential election, he was not satisfied with the process leading up to the election day.
This was revealed in a yet-to-be launched book, 'Against the Run of Play', written by bestselling author Segun Adeniyi.
"I was disappointed by Jega because I still cannot understand what was propelling him to act the way he did in the weeks preceding the election," the book quoted Jonathan as saying.
"As at the first week in February 2015 when about 40 percent of Nigerians had not collected their PVCs, Jega said INEC was ready to conduct an election in which millions of people would be disenfranchised."
The former president also said that at a meeting he had with Jega before the election, he told him that INEC was not ready for the polls but he (Jega) insisted that the election would go ahead as planned.
"Of course, the Americans were encouraging him to go ahead yet they would never do such a thing in their own country. How could we have cynically disenfranchised about a third of our registered voters for no fault of theirs and still call that a credible election?
"The interesting thing was that the opposition also supported the idea of going on with the election that was bound to end in confusion," Jonathan said.
ALSO READ: Jega admits 2015 election was not perfect
The ex-president also defended his decision to shift the election for six weeks - the poll was originally slated for February 14, 2015.
He said the postponement was due to security reasons.
"When the military and security chiefs demanded for more time to deal with the insurgency, the reasons were genuine.
"As at February 2015, it would have been very difficult to vote in Gombe, Adamawa, Borno and Yobe states. But the moment all the arms and ammunition that had been ordered finally arrived, the military was able to use them to degrade the capacity of Boko Haram to the level in which they posed the threat to the election," he said.
In the book, Adeniyi, who is the chairman of THISDAY editorial board, chronicled how an incumbent government lost a presidential election in Nigeria.