Google has started selling adverts on television as the search giant continues to expand its reach to other media, according to reports.

Sources told Wall Street Journal that Google is buying ad time on a small cable service, Astound, in Concord, California, then re-selling commercial breaks to advertisers under an auction system.

A trial began in December and aims to test the firm’s network infrastructure with a view to pushing ads to cable platforms in the round.

Google recently filed patents on technology to deliver ads to billboards and is already trialling radio and print ads for AdWords customers – the printed ads operated using a similar auction system.

But the TV delivery to date uses salespeople rather than computer software to regulate auctions as the technology is currently limited.

If Google can put the juice back into television advertising, it may attract networks like ITV and SMG, which have faced ad slumps in the last couple of years, hit by increasing plurality and the transfer of eyeballs to the internet.

Meanwhile, data out last week showed Google is earning more ad revenue than any UK media company – second only to ITV.