The Scottish firm, which has been involved at nine Olympics and six FIFA World Cups, were by far the most experienced bidder and their withdrawal raises serious question marks about the quality of the back-up power supply in Rio - which is a crucial part of any Games.

Aggreko told investors that contracts for Rio were being awarded separately and that they had been unsuccessful in the opening rounds.

They also cited time constraints with the Olympics due to get underway on August 5.

"Given the preparation required for an event of this scale, we have withdrawn from bidding for the remaining tranche," the company said.

Chief executive Chris Weston added: “We have given considerable thought to our decision to withdraw from the bidding process and I would like to thank our team for all their hard work.

"We wish Brazil, the Rio 2016 Committee and the International Olympic Committee the very best for a successful games.”

A mixture of Brazilian and international firms are reportedly now in the running for the contracts for the generators, which will be used across Games sites.

With the London 2012 temporary power contracts signed two years in advance, Rio organisers don't appear to have time on their side.

"There is increased risk of going somewhere who doesn't have the experience," Will Kirkness, an analyst at Jefferies, told Reuters last week.

Aggreko had supplied the power at Beijing 2008 and London 2012, with their deal in the British capital totalling £37 million ($56 million/€51 million).

Rio 2016 spokesman Mario Andrada told Reuters last week that he was confident in the abilities of the companies still in contention for the tender.