"It was a very bad experience because I didn't understand what was happening.... but everything has turned out as I expected," Mayo told Spanish sports daily Marca.
The 30-year-old Saunier Duval rider, who was subsequently suspended by his team, failed the test on the July 24 rest day of this year's Tour. He finished the race in 16th place overall.
Spanish media said that the Spanish Cycling Federation had told Mayo's lawyer that the 'B' test had been negative.
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Saunier Duval team manager Mauro Gianetti said the team had not yet received any official notification of a negative test.
"We haven't heard anything from the UCI," he said. "We have read stuff on the Internet and it seems that this has happened but it is too early to make any comment."
Mayo said he had been badly affected by the incident.
"I have never stopped training, but psychologically I had a very bad time although people have helped me. I've got a year left on my contract with the team and I hope to complete it."
"It doesn't seem logical nor credible," he said. "It is all rather hypocritical. I've spent many years cycling and I can't chuck it all in but sometimes you feel like it because there are so many injustices.
"The fans who like cycling don't want to see this sort of thing happen."
Mayo, who joined Saunier Duval from the Euskaltel Euskadi team last October, has frequently been tipped to shine in the Tour de France but has failed to live up to expectations.
He finished sixth in the Tour de France in 2003 and won the Dauphine Libere race in 2004.
This year's Tour, which was won by Spain's Alberto Contador, was blighted by a series of doping scandals.
Pre-race favourite Alexander Vinokourov tested positive for blood doping following his victory in the Albi time trial and Michael Rasmussen was sacked by his Rabobank team while in the lead because he had lied about his training whereabouts.
Last month the 2006 Tour de France winner Floyd Landis was stripped of his crown and banned from the sport for two years after a French laboratory found traces of synthetic testosterone in a sample provided by the rider during the race.
Race victory has since been awarded to Spanish rider Oscar Pereiro.
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