The consequences of a weak deal will be felt first and worst by poor nations where climate impacts are already devastating lives and livelihoods, the aid agency CAFOD has said.
The Director CAFOD, Chris Bain, has reiterated that world leaders must agree a legally binding and fair deal at the UN climate change talks. He warned of a "total breakdown" of the infrastructures that offer protection and a future to the poorest people.
It comes as right-wing campaigners and journalists, reviving denial of human-made climate change, are being accused  of trying to derail the Copenhagen climate summit.
Bain said in a statement: "The good work that has been done on improving and empowering the lives of millions of people in the developing world is being hampered by climate change. In the coming years we could see a total breakdown of the infrastructures that offer protection and a future to the poorest people. The progress made in education and healthcare over the past decades could be reversed, with many more children dropping out of school and an increase in malaria and water-borne diseases.
"As climate change worsens in countries like Bangladesh and Kenya, development agencies such as CAFOD will have to put more resources into emergency aid for communities instead of being able to focus on projects that help families function independently into the future.
"If the world's rich nations fail to reach a credible and legally binding deal at Copenhagen that puts the poorest at its core through sufficient financial reparations for the damage we have done to their climates from our own industrialisation, they will force the poorest to the margins of existence.
"World leaders must listen to the poorest people and take strong action at Copenhagen to safeguard their futures and a future for all of us."
CAFOD is calling for rich nations to deliver $195 billion additional finance each year to help the poorest nations adapt to climate change and set them on a path towards a low carbon economy.
The aid agency believes the industrialised nations must commit to a reduction in greenhouse gases of at least 40 per cent by 2020 based on 1990 levels in order to prevent warming reaching the danger level of a global increase of 2 degrees Celsius.