Thousands of volunteers at the Rio Olympics have apparently quit after working long hours during chaotic shifts and not being supplied with enough food.

More than 50,000 people from across the world offered to work for free at the Games, helping with a variety of jobs including chauffeuring athletes around Rio de Janeiro, showing ticket holders into the stands and helping attendees find their way to the sporting venues.

Around 30 per cent of these helpers, however, have failed to show up for their shifts, according to CBC news.

“Many volunteers had to quit because they had to work two weeks in a row, schedules were messed up,” Luis Moreira, a former volunteer who had previously helped with ticketing, told CBC.

“Lots of people quit because of the food. They were told to work eight, nine hours and were only provided with a light snack.”

Mr Moreira said he quit his job as a volunteer this week due to the organizer’s lack of “consideration for people’s lives and welfare”.

Another volunteer, 23-year-old Aisha Marcelina, who drives athletes to and from the Olympic Village, said volunteers are often made to work overtime.

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“They ask us to come to work really early and then hold us back when it's time to go home," she says.

Andreia Barros, 30, told The Wall Street Journal: “I’ve taken off 15 days to dedicate myself to being a volunteer and unfortunately I’m here, without a schedule, at home.”

According to the New York Daily News, only around 35,000 volunteers have continued to show up at the Games.

The problems experienced by volunteers are the latest in a series of issues that have dogged this year's Olympics, which had already been overshadowed by the Zika Virus, water pollution in the pathogen-infested Guanabara Bay and protests by Brazilians over the cost of putting on the Games.

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Olympic organizers, however, have denied that the drop in volunteer numbers is an issue.

“This number allows us to operate at a comfortable level as some volunteers not showing up was factored into our plans,” organizers told the Daily News.

Rio 2016 spokesman Mario Andrada told CBC that they were trying to correct the problems some of the volunteers said they had experienced.