The former Colombian hostage Ingrid Betancourt returned to what she called her "other family" in France today as doubt was cast on the apparently daring rescue that won her freedom.

Arriving to a warm embrace from Nicolas Sarkozy and his wife Carla Bruni, the 46-year-old, who was largely brought up in France as the daughter of a Colombian diplomat and also has French nationality, was welcomed at the Villacoublay military air base near Paris, where she flew in on the French presidential Airbus.

But while she was still in the air, the Swiss radio station RSR broadcast a report questioning the official version of the operation to free Ms Betancourt and 14 other hostages – saying that money, not cunning, had clinched their freedom.

According to Bogota, the hostages were freed in an elaborate ruse by Colombian intelligence agents who had infiltrated the Marxist Farc rebels holding them.

But RSR said that the 15 hostages “were in reality ransomed for a high price, and the whole operation afterwards was a set-up". Citing a source "close to the events, reliable and tested many times in recent years", it said that the United States – which had three citizens among those freed – was behind the deal and put the price at $20 million.

The Colombian Foreign Ministry furiously denied the allegations, with a spokesman calling them "completely false." He added: "They are lies".

General Freddy Padilla, head of the Colombian military, categorically denied they had paid "a single peso" to Farc.

"As the General Commander of the Armed Forces and on my military honour, I deny that the Colombian Government has paid a single peso, a single cent," he said.

Ms Betancourt also cast doubt on the claims. "Based on what I was able to see in this rescue operation, because of the intensity, I don't think they could have fooled me," she said. "I don't think that anyone was acting. The situation was too intense."

The French Foreign Ministry denied any involvement in any deal and there was no sign that the Swiss report would sour the celebrations planned by Mr Sarkozy both at the airbase and later at the Elysee Palace.

Speaking by the steps of the aircraft, Mr Sarkozy publicly welcomed Ms Betancourt to France, telling her that "all of France" had followed her struggle in the jungle and admired the strength of her spirit.

"We ordered in the sun today, because we could not very well welcome you in the rain, could we?" he joked.

In a lengthy reply, Ms Betancourt paid tribute both to Mr Sarkozy – "this wonderful man who has worked so hard for me" – and to her rescuers, for an operation in which "not a single bullet was fired".

Most notably, however, she thanked France for having driven forwards the negotiations that ultimately led to her release – implying, perhaps, that her liberation was the result of more than simply a cunning rescue plan.

"France is my home - you are my family," she said.

Before the allegations of a payments arose, Dana Perino, the White House spokeswoman, said the rescue “was conceived by the Colombians and executed by the Colombians with our full support,” while implying that Washington had provided intelligence and even operational help. The US has not responded to them.

The French Foreign Ministry said it had not paid any money. “Not having been associated with this operation, we could not have been associated with its means of financing, if there were such means,” the Foreign Ministry spokesman said.

French media have also raised questions about Ms Betancourt’s relatively healthy appearance after her release, compared with the gaunt and haggard look of her last video from captivity. French state radio suggested the hostages may have been given food and medicine to return them to health before their release. There was no suggestion that the hostages knew they were to be released.

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