BOGOTA (Reuters) - Former Colombian President Alvaro Uribe, accused of witness tampering and bribery, on Wednesday asked the Senate to ignore his resignation letter so that his case remains with the Supreme Court.

FILE PHOTO: Former Colombian President Alvaro Uribe leaves after addressing the media in Rionegro, Colombia July 30, 2018. REUTERS/Fredy Builes

Uribe, who was in office from 2002 to 2010 and mounted a military offensive against Marxist guerrillas, said on Monday he would resign his seat in the Senate to concentrate on his defense after the Supreme Court called on him to testify.

Uribe, 66, is a mentor of incoming President Ivan Duque, who won the June 17 election as the candidate for Uribe’s right-wing Democratic Center party.

The former president is under investigation by the court over allegations he made false accusations and tampered with witnesses in a case he himself started by making similar accusations against leftist Senator Ivan Cepeda.

Uribe has been accused by political foes of resigning from the Senate so his case can be investigated in the ordinary courts and not in the Supreme Court, which he claims is biased against him.

“I have asked Senator Ernesto Macías, president of Congress, to withdraw, without considering, my resignation letter. For reasons of honor, it has never been in my mind that the Supreme Court won’t hear the case for which they are summoning me to testify,” Uribe wrote in a Twitter post.

Uribe’s lawyers did not immediately respond to a request for comment.

In 2012, Uribe accused Cepeda of orchestrating a plot to falsely tie him to right-wing paramilitary groups during jail visits to former fighters.

But in February the Supreme Court, the body charged with investigating criminal matters involving lawmakers, said Cepeda had collected information from former paramilitaries in the course of his Senate work and that he had not paid or pressured them. Instead, the court said, it was Uribe who was at fault.

The activities continued even after the ruling, the court said in a statement on Tuesday.

If convicted, Uribe could face jail time.

He has remained a polarizing kingmaker in Colombian politics as his party has sought to stymie a peace accord with Marxist rebels. He and his family have long been accused of paramilitary involvement by the opposition, but previous investigations have borne little fruit.

Paramilitary groups in Colombia - originally funded by landowners eager to protect themselves from rebel fighters - became violent organizations connected to drug trafficking, massacres and sexual violence.

The 50-year conflict in Colombia has killed more than 220,000 people.