Ex-prosecutor Franklin Nieves, who fled Venezuela last week, told CNN en Español
on Tuesday that "100% of the investigation was invented" around false evidence in a sham prosecution allegedly orchestrated by President Nicolas Maduro and Diosdado Cabello, the head of the National Assembly.
Lopez was sentenced last month to nearly 14 years in prison and immediately took to social media to say, "This sentence is not only against me, but it attempts to bring down the spirits of everyone who is fighting to have a better country," according to his verified Twitter account.
Jailed since February 2014, Lopez had rallied opposition against what he considered heavy-handed rule by Venezuelan presidents.
Nieves said in an interview that he received orders from government officials to arrest Lopez two days before a 2014 opposition march.
He told CNN's Fernando del Rincon, "They jailed him because they fear his leadership."
The former prosecutor said that "after examining each and every piece of evidence it was shown that this person had at no point made even a single call to violence."
Video from anti-government protests where Lopez spoke show him "always calling on his supporters to remain calm," Nieves said.
Witnesses made false statements against Lopez, who was not permitted to adequately defend himself, said Nieves.
Venezuela's Ministry of Communications and Information has not responded to CNN requests for comment, but the nation's ombudsman, Tarek William Saab, told CNN that Nieves should have made his allegations during the trial and not afterward and Venezuela's chief prosecutor, Luisa Ortega Diaz, denied that Nieves was pressured to go after Lopez.
But Nieves said that the actions against Lopez are not uncommon in Venezuela.
"There are innumerable cases in which people were investigated and innocent people detained," he said.
Nieves said he had not spoken out earlier "out of fear" and because of the "pressure exerted" by superiors to get prosecutors to act "on the whims" of the government.
Lopez's wife, Lilian Tintori, said Nieves' accusations highlight the state of justice of Venezuela.
"Justice has been kidnapped, with the regime's henchmen unfairly making accusations against, imprisoning, torturing and persecuting the leaders who represent hope in Venezuela," she said.
Nieves' comments come one week after defense attorneys for Lopez appealed the sentence against the 44-year-old economist.
Human rights activists and the U.S. government decried the sentence against Lopez.
The court said Lopez committed serious crimes, according to Venezuelan state news agency AVN
-- public instigation, vandalism, arson and criminal conspiracy.
But legal proceedings were a sham, Human Rights Watch said.
"The baseless conviction ... exposes the extreme deterioration of the rule of law in Venezuela," the rights group said in a statement. "The trials involved egregious due process violations and failed to provide evidence linking the accused to a crime."
U.S. Assistant Secretary of State Roberta Jacobson said last month that the conviction "deeply troubled" her and called on the Venezuelan government to protect democracy and human rights.
In a four-page letter after his sentencing, Lopez said he was writing from the military jail of Ramo Verde. He urged all Venezuelans to instigate a "democratic rebirth" by making their voices heard in the country's next parliamentary elections.
The accusations against Lopez stem from opposition street protests in February 2014 that turned deadly. Dozens of people were killed, and hundreds injured.
Maduro, the handpicked successor to the late President Hugo Chavez, blamed Lopez, accusing him of terrorism and murder. Lopez was already a strong government critic
before Chavez's death in March 2013.
In 2008, Chavez's government banned Lopez, a former mayor, from running for office.
But much of the violence at the 2014 protests stemmed from security forces, which also arrested hundreds, Human Rights Watch said. Security forces were accused of torture and abuse.
"The government has also tolerated and collaborated with pro-government armed groups of civilians," the group said.
Lopez briefly went into hiding but then turned himself in to authorities. He used social media to rally supporters who met him on the occasion.
A court said last month that Lopez's involvement in protests was part of a plan for a coup d'etat.
In June, Lopez went on a 30-day hunger strike in prison to demand congressional elections. The government has agreed to the demand, and elections are scheduled for December.