A UN report says it will cost up to $1bn and take 30 years to clean up the damage done by decades of drilling by Shell.

Oil exploration in Nigeria's south for several decades has had a debilitating effect on the environment of the region.

Shell, the Anglo-Dutch oil company, has been accused of serious failures in its handling of the pollution in the Niger Delta and shirking its responsibility.

Activists have demanded that Shell's licence be revoked for the environmental disaster.

But with 90 per cent of the government's revenue coming from petroleum exports, oil companies seem to have clear political leverage over the issue.

Al Jazeera's Yvonne Ndege reports from southern Nigeria.