But despite this increase, the actual rate of growth is gradually slowing and will continue to do so in future decades.

However, in its annual report on the state of the world population, the UNFPA say that there needs to be continued action.

The agency is calling for more money to help fund spending on health care programmes and reproductive education.

It says that a lack of funds could result in "millions of additional unintended or unwanted pregnancies . . . tens of thousands of additional maternal deaths, and at least a million more infant and child deaths."

The agency also warns that high birth rates in past years mean that there are now more people than ever entering their child-bearing years.

The charity estimates that more than 90% of population growth in the future will take place in the developing world. In the least developed countries, such as in parts of Africa more than 43% of the population is between the ages of 10-19.

In European countries fertility and mortality have dropped gradually over the past 150 years. But in some parts of the developing world while improvements in health care have reduced mortality and increased life expectancy, fertility has declined more slowly leading to large population growth.

The charity is calling for better health programmes to address the needs of young people in particular. The agency wants improved access to contraception and counselling combined with better education about how to avoid pregnancy and sexually transmitted diseases.

There has also been rapid growth in the number of people over the age of 65. More than 95% of this growth in the next 50 years will take place in developing regions like India. But in the same period the percentage of the population over the age of 65 in developed countries like Japan, Italy and Germany will hit 40%.

This growth in the number of both young and old dependent citizens places strains on each society. The report points out that many governments find it hard to provide education and health care for the young along with the support and medical care the elderly need too.

The report says that although there is some form of support for the old or disabled in 155 countries - it only covers 30% of all the people aged over 60.