The number of UK households with digital television on their main set has risen to 21.7 million, according to a new report by Ofcom.

In its Digital Television Progress Report for the third quarter of 2007 (July to September), the regulator found that Freeview boxes were driving the digital growth.

During the same quarter 2.4 million Freeview devices had been sold, up from 1.4 million from the same period for 2006.

Ofcom said 8.6 million set-top boxes or TV's with integrated Freeview had also been sold over the past year, compared to 5.8 million in 2006.

However, it was pointed out that digital growth could not just be attributed to Freeview as Sky had also increased its customer base by 67,000 during the third quarter of 2007 to more than 8.1 million. Sky’s high-definition service also added 66,000 subscribers during the same period, taking the total number to over 350,000.

The total number of homes with cable TV, including Virgin Media, also continued to rise, with over 3.4 million subscribers at the end of the reported quarter, a figure up by over 100,000 homes year-on-year.

Ofcom's report also found that people were now upgrading their secondary television sets, having already converted their primary television sets to digital. The total number of second television sets converted to digital now stands at nearly 12 million, up by 1.3 million during the third quarter of 2007.