By Julia Symmes Cobb
BOGOTA, May 5 (Reuters) - An election campaign advisor to Colombia's President Juan Manuel Santos resigned on Monday amid allegations that he took a $12 million bribe to prevent the extradition of a suspected drug trafficker to the United States.
Venezuelan political guru JJ Rendon, one of several advisors to Santos, denied the accusations in a statement, and said they were part of a plot to tarnish the reputation of the president ahead of elections on May 25.
"I have decided to voluntarily resign from my post so as not to be turned into an instrument of the enemies of peace who seek to destroy the credibility of the president," Rendon added.
Rendon, a staunch critic of the socialist government in his native Venezuela, advised Santos during his first presidential campaign in 2010 and also worked for Mexican president Enrique Pena Nieto during his election campaign in 2012.
Santos told a local radio station on Monday that Rendon had relayed an offer of surrender from the alleged traffickers, but that no deal had been reached because the men had refused to turn themselves in to the authorities.
"I believe has said that he didn't receive one peso, and until I'm shown the contrary, I think he has to be believed," he said.
Weekly news magazine Semana published on Saturday testimony from Javier Antonio Calle Serna, a member of the Rastrojos crime gang who surrendered to U.S. authorities in 2012, saying that he had paid Rendon $12 million to lobby government officials to prevent his extradition and that of three other traffickers.
Rendon said in his statement that he had "never received a cent".
Santos is widely expected to be elected to a second, four-year presidential term. He initiated peace talks with the Revolutionary Armed Forces of Colombia (FARC) rebels 18 months ago in an effort to end a 50-year-old conflict that has killed more than 200,000 and says he needs a second term to cement the deal. (Additional reporting by Luis Jaime Acosta; Editing by Peter Murphy and Miral Fahmy)