By Duncan Mackay in Copenhagen
September 30 - The battle to host the 2016 Olympics turned ugly here tonight after Rio de Janeiro formally complained to the International Olympic Committee (IOC) after an official from Madrid reportedly criticised the Brazilian city as having "the worst bid" of the four candidates.
Spanish Olympic Committee vice president Jose Maria Odriozola allegedly made the comments to Spanish news agency Efe.
He said: "The IOC is not going to risk it and take the Games to a site where it doesn't have total confidence that it can be done well."
Rio bid organisers said the criticism was "totally unacceptable" and have filed a complaint to the Ethics Commission, who will adjudicate.
The list of penalties they can impose range from a warning to expelling Madrid from the race to follow London 2012 and host the Games, which also includes Chicago and Tokyo.
A spokesman for Rio 2016 said: "This gentleman is clearly out of step with the report of the IOC's own Evaluation Commission."
Odriozola, who is also President of the Spanish Athletics Federation, has been appointed by the International Association of Athletics Federations (IAAF) as the technical delegate for track and field at the London 2012 Olympics and is a hugely-respected figure internationally.
The row flared-up two days before the IOC votes to decide which city will host the 2016 Games and less than 24 hours after Olympic officials reminded the four candidate cities not to target rival bids.
Mark Adams, the IOC's Communications Director, said: "We would remind all cities that they must be careful of what they say.
"They must not criticise other bids."
The comments by Odriozola (pictured) were reported as the Spanish team travelled to Copenhagen, the last of the quartet to arrive for final lobbying.
The IOC's Evaluation Commission issued a report this month after visiting all four candidates earlier this year.
Experts considered Rio to have received the best report and that they were now the favourites, ahead of Chicago, to be chosen to host the Games.
Rio's complaint is being directed to French lawyer Paquerette Girard Zappelli, who is secretary to the eight-member ethics panel which monitors bidders' behaviour.
The panel includes four IOC members and four people from outside the organisation, including Javier Perez de Cuellar, the former United Nations Secretary-General.
It is the second row between Rio and Madrid.
Earlier this year, Rio threatened to report Madrid to the Ethics Commission after they claimed they had sent a "spy" during the Evaluation visit in April.
Simon Walsh, a British-based freelance journalist and consultant who had been working for Madrid 2016 and whose name regularly appeared at the foot of press releases, was stripped of his media accreditation and refused entry to the final IOC press conference because Rio officials claimed he had lied about who he was working for.
Walsh was accredited here for Efe but Rio alleged he had actually been sent by Madrid to provide intelligence reports.
In the end, Rio decided not to take any further action but the row soured relations between the two cities.
Contact the writer of this story at [email protected].
May 2009: Madrid claim they never intended to spy on rivals Rio
May 2009: Spy row erupts between Rio and Madrid