The International Olympic Committee ensures adverts or logos of products are not visible in the fields of play in line with its Olympic Charter despite sponsors paying hundreds of millions of dollars to be associated with the Games.
The Minis, made by German car manufacturer BMW who is also Games sponsors, may not carry visible logos but are instantly recognizable for what they are.
However, they are not the iconic British-owned Minis produced from 1959-2000 but the new type produced by BMW.
"There is no commercial reason (behind choosing Minis)," said Timo Lumme, the IOC's director of TV and marketing services on Tuesday when asked by reporters if branding rules were being broken.
He said the choice as transporters for the athletes' equipment was not dictated by a commercial decision.
Since the start of the athletics competitions last week, the Minis have instantly become a point of discussion with their use inside the stadium raising the questions of whether the IOC was indirectly relaxing its own strict ad rules.
He said the International Association of Athletics Federations, responsible for the track and field competitions at the Olympics, had cleared the use of the small vehicles.
"IAAF validates several different transporters. Yes, it happens to be the official partner of the London Games but there is no commercial delivery," he told a news conference.
"There is no link between the sponsorship and the coverage of the physical fact that these are mini Minis on the field of play," Lumme said.
The IOC's rule on advertising states that no form of advertising or other publicity shall be allowed in and above the stadia, venues and other competition areas which are considered as part of the Olympic sites.
Commercial installations and advertising signs are not be allowed in the stadia, venues or other sports grounds.
There are three of these vehicles in total. Each puts in four-hour shifts across nine days of athletics competition, covering six kilometers per day.
The Mini also featured in the Games opening ceremony but again it was the new version and not the one symbolizing iconic British post-war design.
"The bottom line is that the producer showed an individual quirkiness, a fantastically entertaining take on British history," said Lumme of the car's presence in the opening ceremony.
"The Mini is an incredibly known globally, British icon. Again Rule 50 compliant. No logos," he said.
The London Games have received some 700 million pounds ($1.09 billion) from sponsors wishing to be associated with the 2012 Olympics.