Venezuela's Gonzalez says he was forced to sign letter accepting court ruling of Maduro victory
"Either I signed or I faced the consequences," he said in a statement.
Gonzalez is currently in Spain, where he was granted political asylum earlier this month following the issue of a warrant for his arrest in Venezuela.
The national electoral council proclaimed Maduro the victor of the July 28 presidential election, prompting allegations of fraud and widespread protest as the opposition published vote tallies online that they said showed Gonzalez had won.
Earlier this week, a U.N. report said Maduro's government escalated repressive tactics to crush peaceful protests and keep power in the aftermath of the South American country's disputed election.
The declaration by Venezuela's top electoral authority was approved by the country's Supreme Court, even though officials have not published vote tallies showing Maduro's victory.
Gonzalez said he was met at the Spanish embassy in Caracas by Venezuelan Vice President Delcy Rodriguez and her brother Jorge Rodriguez, president of the National Assembly, who gave him the letter to sign.
"There followed very tense hours of coercion, blackmail and pressure," Gonzalez said, adding he felt he would be more useful in freedom than locked up.
"A document produced under duress is totally worthless, due to a serious lack of consent," the statement added.
In Caracas, Jorge Rodriguez presented a two-page letter signed by Gonzalez and said the former presidential candidate, 75, had 24 hours to retract his claims.
"If you don't deny that in 24 hours, I'm going to release the audios, it's up to you, Mr. Gonzalez," Rodriguez said, referring to the meetings he and his sister held with Gonzalez.