He also announced a new set of priorities to ensure the quangos “relentlessly focus” on fighting the recession.

But the Conservatives plan to scrap the NWDA and the other RDAs, handing their powers to local councils.

If the Tories win the next general election, the NWDA’s key powers over housing, planning and economic strategy would be lost.

Lord Mandelson said: “We have clear evidence RDA programmes are helping to drive regional economies, creating jobs, helping businesses and boosting skills.

“They are on the front line of our response to the global downturn. But their medium and long-term interventions and investments are equally important to prepare for the upturn. It will help ensure that we emerge stronger.”

That message was echoed by NWDA chief executive Steven Broomhead, who said: “This report has provided the most comprehensive independent evaluation of our investments since our inception.

“It is very positive to see many of the projects and initiatives evaluated have had a real and significant impact on regional economies. Importantly, these results only demonstrate part of our impact – we know there will be more value to come.”