From the horse's mouth.

The national identity card is likely to be counterfeited, police have warned, see here.

At present there would appear to be about 12 card readers available in the UK to verify the authenticity of ID cards. As a result detective chief superintendent Nigel Mawer of the Metropolitan Police no less, states that:

As with any form of identification, it's likely that the ID card scheme would be targeted by people creating false IDs...It's important that people invest in the equipment to enable them to tell if an ID card is genuine, to get the full benefit from an anti-crime perspective.

Detective chief inspector Nick Downing adds:

The cards are not widely distributed at the moment, and the Met has yet to see any fakes....but if the cards do come in across the UK, we will see them being counterfeited.