In the UK the number of households under ‘water stress’ will increase to almost a quarter of the population as the average temperature rises by up to 3C in the south.

This means that by 2100 18 million people will be at risk of ‘not having enough water to meet their daily needs’.

Water stress will be worse in South and South East, where there is already a problem providing the growing population with enough water.

This winter water companies in Anglia, South East Water and Severn Trent have declared themselves in drought and are asking consumers to limit water use. It is expected the South East and Midlands will face a hosepipe ban next summer following the driest 12 months on record in some areas.

At the other end of the scale the risk of costal and river flooding will also increase because of rising sea levels and more heavy bursts of rainfall.

The Met Office estimated that there will be a “general increase in flood risk for the UK”.

The projections ranged from a three and a half times greater risk of flooding to a decrease in flooding by a fifth.

This complex picture was also reflected in the impact on agriculture.

Although the maximum area of land that will increase in suitability was 99 per cent, there was one study that found it will decrease by a fifth.

Northern Ireland and Scotland are expected to see the biggest boost in crop production, while the south of the country may suffer from drought.

Overall the Met Office estimate that crop production in the UK will increase by 96 per cent, citing studies that predicted an increased production in wheat, soybean and sunflowers as temperatures rise.

However Jonathan Scurlock, of the National Farmers Union, said a number of other factors have to be taken into account such as the increased risk of droughts and floods.

The report admits that disease, pollution and increased levels of carbon dioxide in the atmosphere have also not been taken into account.

“The implications for agriculture generally are negative in the long term,” said Mr Scurlock. “If nothing is done now we are looking at significant impacts in a generation’s time.”

The report estimated that the production of staple food crops will decrease in parts of Bangladesh, Brazil, China, Egypt, India Russia, Turkey and the USA.

A recent Oxfam have warned that food prices are already rising as a result of reduced crop yield around the world due to climate change and warned the problem could drive malnutrition in future.

Chris Huhne, the Energy and Climate Change Secretary, said that overall the impact of climate change could be extremely damaging for the UK and the world.

“This report highlights some of the very real dangers we face if we don’t limit emissions to combat the rise in global temperature. Life for millions of people could change forever, with water and food supplies being placed in jeopardy and homes and livelihoods under threat. This makes the challenge of reducing emissions even more urgent,” he said.

The report warned that if the world does not limit temperature rise to 2C by cutting carbon emissions then the majority of countries are projected to see an increase in river and coastal flooding, putting 49 million more people in danger by 2100.

The Lib Dem minister arrived at the United Nations talks in Durban yesterday (Monday) to try and persuade the rest of the world to sign up to ambitious carbon emissions, despite the fact that his own Government is being criticised for rowing back from climate change back home.

Mr Huhne wants the world to agree to work towards a legally binding deal by 2015 that would commit all countries to cutting emissions.

But at the moment the US, China and India are refusing to sign up, raising fears that the talks could collapse.

“The UK wants a legally binding global agreement to keep the global temperature rise below 2C,” he said. “If this is achieved this study shows that some of the most significant impacts from climate change could be reduced significantly. By the end of the week we need to see progress to move towards this goal.”

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