Duncan said the time is right for a new push to digital switchover now Freeview is established. His comments follow speculation that the government's planned date for the analogue switch-off, 2010, is unachieveable in the wake of ITV Digital's collapse.
He revealed that sales of Freeview adapters have passed 500,000 since it launched last October.
Duncan also said Barb figures for March will show there are 1.4 million Freeview households compared with a peak of 1.2 million ITV Digital households.
The figure includes new Freeview viewers as well as those using old ITV Digital boxes.
Duncan attributes the success of Freeview to it being a simple proposition that involves a one-off payment and no contract.
He said evidence suggests Freeview appeals to new consumers, who would not watch pay-per-view TV, including older upmarket viewers, and those who cannot afford pay-per-view.
Duncan's comments coincide with MindShare research that shows more than half of the set-top box/digital adapter viewers watching Freeview are 'digital virgins'.
MindShare says that this group is pleased with content such as 24-hour news but believes there are too many repeats.
These viewers make up one of three groups identified by the research.
Another group, consisting of former ITV Digital viewers, "do not seem overly satisfied with the choice of channels".
The third group bought Freeview to upgrade a second TV in a Sky/cable home.