The World Bank said on Friday that more public investment is needed in Kenya's urban areas.

World Bank Senior Director for Social, Urban, Rural and Resilience Global Practice Ede Ijjasz-Vasquez told a media briefing in Nairobi that at current water and sanitation coverage expansion rates it would take more than 20 years to reach universal coverage.

"Much more public investment is required in order to close the service delivery gap," Ijjasz-Vasquez said during the launch of the Kenya Urbanization Review which looks at Kenya's urbanization to date as well as prospects for the future.

The review is among the studies the World Bank is undertaking across the globe, including in several countries in Sub-Saharan Africa. Ijjasz-Vasquez said that out of Kenya's total population of 44 million only 12 million people live in urban areas.

He said that access to clean water is particularly lagging behind in many urban areas.

"Current water demand in the Nairobi and Mombasa outstrips supply by 150,000 and 100,000 cubic meters per day, respectively," he said.

The World Bank noted that only about 18 percent of urban population is covered by a proper sewer system and existing waste treatment plants operate at about 15 percent efficiency leaving most effluent untreated.

The financial institution noted that particular attention needs to be paid to the inequity in access to services that is found between urban areas and within urban areas.

The senior director said that Kenya's larger urban areas, as is true in most developing countries, generally have better access to urban infrastructure services than do small ones.

Ijjasz-Vasquez said that the lack of public investment in infrastructure increases the cost of developing housing since these costs are often then borne by the developer.