Computer engineers were at a loss last night to explain why the Government had been hit by arguably the worst electronic meltdown in the history of Whitehall.

Senior sources said that the specialist troubleshooters called in to deal with the crisis at the Department for Work and Pensions (DWP) had failed to "get to the bottom" of the problem which blanked out up to 40,000 desktop screens.

While it has been established that the crash was provoked by an attempt to upgrade the screens, there was still no precise idea why it happened.

As the Government tried to play down the impact of the problems, Conservatives and union leaders demanded an immediate inquiry into a crash that affected one of the country's biggest IT networks.

Full Report: The Independant