CAFOD's Brazil Programme Officer said: "Indigenous peoples are being murdered, criminalised, threatened, evicted from their land, and their rights to health and education are systematically violated.
"The Rio Olympic Games are a huge missed opportunity to improve the lives of the poorest in Rio.
"They are also a missed opportunity to invest in the protection of human rights across the country."
Tuesday 9th August marked the United Nations' (UN) International Day of the World's Indigenous People and the organisation has said the risks that indigenous peoples in Brazil face to their lives are "more profound than at any time since the adoption of the Constitution in 1988".
A Yanomami community member in the Amazon uses a water filter installed with CAFOD funds in response to droughts and fires in Yanomami indigenous territory in March 2016.
Streams in Yanomami Indigenous Territory in the Amazon rainforest have been polluted with mercury from small-scale illegal gold mining.
On 14th July 2016, CAFOD's partner, CIMI Tefé (Indigenous Missionary Council) organised a demonstration of indigenous leaders in defence of their rights, and presented a petition to the authorities demanding effective implementation of public policies.
Esther Gillingham said that the Brazilian government is proposing constitutional amendments which specifically harm indigenous communities.
She told Premier: "One of the biggest ones [constitutional amendments] is PEC215, which will give anti-indigenous landowners the chance to block the recognition of new indigenous territories, so this is actually detrimental as land is key to indigenous people's survival and sustainability.
"With Brazil being in the world spotlight during the Olympics, many people don't realise this is happening.
"So even just to raise awareness and to show that these people are being threatened and marginalised, and that we have a role to play is incredibly important."
The majority of Brazil's indigenous communities live in the Amazon basin and have a spiritual connection with nature which is at risk due to illegal gold mining, and the expansion of large-scale farming and logging.
Around £3.8 billion of Brazilian taxpayers' money is being spent on the Olympic Games.
Listen to Premier's Hannah Tooley speak to Esther Gillingham here:
