The report by the UN's Habitat agency, says poverty remains common in village and rural populations. It says that city slum dwellers are equally disadvantaged and in many cases are in even greater misery and destitution than those in rural areas.

“Around the world the wealthy have created an architecture of fear by retreating behind fortified residential enclaves,” the report says and notes that “gated communities run counter to the fundamental principles of sustainable urban development”.

"We are showing that slum dwellers that represent today one out of three of the total inhabitants in urban areas in the developing world will die earlier than the rest of the population of the city," said one of the authors of the report, Eduardo Moreno. "They do not have the same opportunities in terms of education, access to health. They have less possibility of getting a job and they are suffering from many illnesses."

The report analyses more than 200 of the world's cities. Globally, it says the slum population will swell by 27m people each year over the next 20 years - the vast majority in the developing world, which will have to absorb 95% of all urban growth. Habitat says that urban growth rates are highest in sub-Saharan Africa, where over 70 percent of the urban population lives in slums that often lack access to water and sanitation.

In countries such as Bangladesh, Ethiopia, Haiti and India, it finds child malnutrition in slums is comparable to that of rural areas. But, in many African cities, children living in slums are more likely to die from water-borne and respiratory illnesses than rural children. It says, women living in slums are also more likely to contract HIV/AIDS than their rural counterparts.

Co-author of the report, Nefise Bazoglu, says people do not have to live in such squalor. She says countries such as Egypt, Thailand and Tunisia have managed to reduce slum growth in the last 15 years and have made considerable investments in improving slums.

"Go to a slum area and then sort out the land ownership issue and bring water and sanitation and provide services, technical assistance for building sturdy houses because most of these houses are prone to disasters-floods," said Bazoglu. "You must have read in media that the first victims of floods or fires or whatever they are, are slums."

The report says that countries do not have to be wealthy to get rid of their slums. It says some low- or middle-income countries, such as Brazil, Colombia, Philippines, Indonesia, South Africa and Sri Lanka, have managed to prevent slums from growing through good housing and employment policies.