A child born captive in a rebel camp is at the centre of a bitter dispute between Colombia's government, which says the boy was abused and then freed, and Marxist guerrillas who say they still have him in the jungle.

DNA tests have been ordered to see if the government's theory is correct that four-year-old Emmanuel, born to a kidnapped politician and a rebel father, is in the hands of child welfare authorities.

Rebel leaders of the Revolutionary Armed Forces of Colombia, or FARC, say Emmanuel is still under its guard along with his mother Clara Rojas, who was captured during her 2002 vice presidential campaign.

She, her son and Consuelo Gonzalez, a lawmaker kidnapped in 2001, were supposed to be freed last week in a deal brokered by Venezuela's left-wing president, Hugo Chavez.

The deal crumbled on Monday with the FARC accusing conservative President Alvaro Uribe of ordering disruptive army operations in the jungle area designated for the hand-over, a charge he dismisses.

Emmanuel, who was already a symbol of the young victims of Colombia's guerrilla war, became a national obsession this week when Uribe said he was mistreated by his captors and may have been secretly turned over to foster care in 2005.

"Emmanuel is Colombia's Elian Gonzalez," said Bogota-based political commentator Ricardo Avila, referring to the saga of a young Cuban shipwreck survivor who sparked an emotionally- and politically-charged custody battle in 2000 between his Miami relatives and his father in Cuba.

"If the government's account is correct, Emmanuel was poorly taken care of while in captivity and this could further damage the FARC's image," Avila said.

The FARC holds more than 700 hostages, most of them civilians, and uses them for ransom and political leverage as part of its four-decade-old insurgency.

Guerrilla leaders and Chavez say they want to reactivate the hostage liberation plan, but it is on hold until authorities establish the identity of the child who Uribe says may be Emmanuel and who now lives in the capital city Bogota.

Uribe's credibility could be hurt if the child turns out not to be Emmanuel. DNA samples are being taken from the boy and Rojas' mother to see whether he is her grandson.

Emmanuel's name and other details of his life in guerrilla custody were revealed last year by a police officer who escaped the rebels after eight years in captivity, sometimes in the same camps as Rojas and her son.

He said they were held in rough conditions, often restrained, pestered by insects and fed poorly.

Rojas, a centre-left politician now 44 years old, was snatched during her campaign almost six years ago along with her running mate, presidential candidate Ingrid Betancourt, a French-Colombian national who is also still languishing in captivity.