Climate victims will double - Oxfam

The charity predicted the number affected by events such as flooding, storms and drought would rise from 242 million people to hit 375 million a year by 2015.

And with the humanitarian aid system already a "postcode lottery on a global scale", it is already barely able to cope with current levels of disasters and could be overwhelmed by increases in the next few years, Oxfam warned.

The aid agency said the expected rise of 133 million at risk stemmed from a combination of existing poverty and people migrating to densely populated slum areas which would be prone to increasingly frequent climate-related crises.

The predicted 54% rise in the numbers affected does not include those who may be hit by other disasters such as volcanoes or earthquakes. And it does not include those affected by war, although there are concerns that an increasingly volatile climate could lead to rises in conflicts.

Oxfam is calling for fundamental reform of the aid system, so that emergency aid is delivered swiftly and impartially after a disaster, instead of on the basis of political or other unfair preferences as is often currently the case. The charity also wants national governments, backed by the international community, to invest more in reducing the risk from disasters - as countries such as Mozambique, Cuba and Bangladesh have done.

A new campaign by Oxfam, Here and Now, aims to tackle climate change and ensure the world's poorest and most vulnerable people get a fair deal as the world tackles global warming.

The campaign is calling on rich countries to commit to cuts in greenhouse gas emissions that will ensure warming remains as far below 2C as possible, and to provide at least 50 billion US dollars (£34 billion) a year to help poor countries adapt to climate change.

Barbara Stocking, Oxfam's chief executive, said: "The humanitarian system is a postcode lottery on a global scale. The response is often fickle - too little, too late and not enough. The system can barely cope with the current levels of disasters and could be overwhelmed by a substantial increase in the number of people affected."

Climate and Energy Minister Joan Ruddock said: "Oxfam rightly points out that climate change is not tomorrow's crisis and is already affecting millions of people across the world. The UK is working with vulnerable and developing countries to help them cope with the challenges of climate change, and to minimise the risks to their future development."