Climate change is the biggest health threat of the 21st century, with rising temperatures likely to increase the spread of tropical diseases, according to a new report.

The report commissioned by the University College London and The Lancet said that doctors should put pressure on global politicians as the world’s poorest people will be hit first.

The report said that there will be increased problems with food supplies, clean water and sanitation, especially in developing countries.

The appeal to take immediate action comes before the United Nations climate change conference to be held in Copenhagan this December, which aims to design a comprehensive climate treaty to replace the 1997 Kyoto Protocol.