The D6 format was trialled at the Birmingham Bullring, followed by an initial launch at London rail stations last summer.

The 65in high-definition screens will be positioned within 18 UK shopping centres, including Bluewater, Lakeside and Merryhill. The first of the new screens are up and running in the Centre:MK in Milton Keynes and the full network should be completed by the end of November.

A spokesman said that the digital outdoor sector has risen 60% over the past two years, partly due to organic growth, and partly down to increasing numbers of sites. However, the sector may well experience a temporary plateau over the next few months as the devices are prohibitively expensive, while the outdoor market is currently suffering from the effects of recession on the advertising markets.

This has meant that new digital sites have to take over key advertising positions. "You have to be sure it's in the right place," said the spokesman. However, he added that he didn't see digital as replacing printed outdoor ads. "Our philosophy has always been to persuade advertisers to use digital and traditional ad formats side by side," he said. "Only 9% of all money spent on poster ads goes on digital."

He added that digital billboards can also attract new advertisers to the sector to the benefit of both digital and print media. But he said that digital still offered unique benefits, such as being able to change creatives almost on the fly.

The company claimed that research it commissioned showed that moving images are more eye-catching than their static equivalent, resulting in viewers spending 60% longer viewing them.

Titan Outdoor plans to complement the sites within its two existing networks with smaller format digital screens in the near future.

Jon Slatkin, chief Eexecutive of Titan UK, said: "We've been delighted with the success of D6 in our rail environment and believe this will be emulated across premium shopping malls, offering advertisers the opportunity to enhance their six-sheet campaigns with added standout and flexibility."