PARIS, Dec 7 (Reuters) - French secret agents have contacted Colombian guerrillas holding French-Colombian politician Ingrid Betancourt, a spokesman for French President Nicolas Sarkozy said on Friday.

Sarkozy has stepped up his efforts in recent weeks to secure the release of Betancourt, sending radio and television messages this week to the leader of the Marxist rebel group holding her, urging him to set her free.

Betancourt was seized by the Revolutionary Armed Forces of Colombia, or FARC, during her presidential campaign nearly six years ago and Sarkozy has made her freedom a priority.

Colombia released footage last week of a gaunt-looking Betancourt and other hostages in a secret jungle camp, sparking an outcry.

Sarkozy's spokesman David Martinon confirmed France was in touch with the FARC, telling a weekly news briefing: "Yes we have agents who have entered into contact with the FARC".

"But it's obviously an extremely difficult mission because, you can imagine, to get in touch with the FARC you have to march," he said.

He declined to elaborate, citing security concerns.

In his message to FARC leader Manuel Marulanda, Sarkozy said he condemned the group's methods and did not share their ideas, but urged them to release Betancourt to her family in time for the Christmas holiday season on humanitarian grounds.

In response, the FARC told Sarkozy to stop criticising them if he wanted Betancourt and other hostages freed. It welcomed his involvement in the case but said Betancourt could only be exchanged for FARC prisoners held in Colombian jails. The rebels want Colombian President Alvaro Uribe to demilitarise a rural area the size of New York City for 45 days of talks on a hostage deal. He has refused, saying it would allow the FARC to regroup. The FARC says it is fighting for socialism, but it finances its war with cocaine trafficking and even leftwing Colombian politicians say the group has scant popular support. (Reporting by Jon Boyle; Editing by Catherine Evans)

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