Why does DSG use more fuel?

Could you please explain why a VW Golf with a DSG gearbox will use more fuel than one with a conventional manual box? I can understand why a 'normal' automatic gearbox uses more fuel, because of losses in the torque converter, but as far as I can see the DSG is just a computer-controlled manual gearbox, albeit with a twin clutch system and so on. I am obviously missing something!
Graham Berry

Some versions of the new Golf equipped with DSG 'boxes will increase fuel economy over the manual, whereas others will lower it.

The figures you're looking at probably relate to the 2.0 TDI model, which will use the old six-speed DSG gearbox. This set-up uses two 'wet' clutches, compared to the manual car's one 'dry' clutch, so it will weigh quite a bit more. This will harm both fuel economy and carbon dioxide emissions.

However, the new 1.4 TSI 160 will use the new seven-speed DSG gearbox. This system will use two 'dry' clutches, and as a result the unit will weigh less than the old six-speed 'box. The extra gear will also allow the engine to turn over slower when at high speeds.

Combined with the DSGs ultra-efficient gearchanges, this will mean better fuel economy and lower CO2 emissions than the manual car.