West Wales and the southern valleys have become poorer, despite receiving billions in European Union funding, says a BBC report.
The BBC said it had seen figures showing the region was one of a handful of places to get poorer after two rounds of funding.
More than £6 billion ($11.9 billion) of European money and matching funds from UK, Welsh and local governments had been invested.
The figures were obtained by BBC Wales' Dragon's Eye programme.
Welsh Labour MEP Derek Vaughan told the BBC it was clear that the earliest years of the funding, known as Objective 1, were not properly managed.
