Figures published by market analyst CACI this week reveal that the ten lowest-earning areas of the UK are in the north of England and Glasgow.
Average income in Birkenhead, Leicester and Middlesbrough is £13,000, less than half the UK average of £31,000, the study notes.
The ten highest earning areas are all in London or its commuter belt, with Fleet in Hampshire recording the highest average income of £64,000.
CACI business development director John Rae said: "Although a north-south income divide still exists, the picture becomes far more complex at postcode level, with unexpected pockets of wealth. This presents a challenge for planners who need detailed knowledge to support strategic business decisions."
Wealth of the Nation 2005 can be viewed via www.PlanningResource.co.uk.