Environmentalist Marina Silva joined the likes of Muhammad Ali and United Nations secretary-general Ban Ki-moon who brought the flag (pictured top) into Olympic Stadium in front of 80,000 spectators, leaving Brazilian officials furious at what they perceived as an embarrassing snub.

Silva fell out spectacularly with current president Dilma Rousseff when the pair were both in the Government of Luiz Inácio Lula da Silva.

When Rousseff succeeded Lula, Silva formed the opposition Sol party.

Yet she was the one invited to carry the flag in front of an estimated global audience of one billion, leaving Brazilian Government officials up in arms.

"I didn't know she was here," Rousseff was quoted as saying in the Brazilian media, while Sports Minister Aldo Rebelo went even further suggesting Silva's image as "a sweetheart of the aristocracy" may have played a part.

Marina Silva helped carry the Olympic Flag at the London 2012 Opening Ceremony

But today, International Olympic Committee (IOC) spokesman Mark Adams played down any suggestion of organisers playing politics, pointing out that Silva was chosen because of her fight against the destruction of the Brazilian rainforest.

"The Olympics is non-political," said Adams.

"In certain cases politicians come but they come representing the Olympic Movement rather than a particular party."

London 2012 organisers re-iterated the reasons for Silva's invitation.

"Marina was selected on the basis of environmental work and campaigns to protect the Amazon Rainforest and other environmental issues, and was representing the environment pillar of the Olympic Movement," the organisation said in a statement.

"Her work for the environment has been globally recognised and the IOC was fully aware  of  Marina's selection to help carry the flag."

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