According to Envisional, Britain accounts for about one-fifth of TV downloads through file-sharing networks such as BitTorrent and eDonkey, more than any other country, followed by Australia and the United States.
"Because there's such a demand for US TV, the UK is going to be the main downloader," said Envisional research consultant David Price.
Popular US television shows such as "The West Wing," "The Sopranos" and "Friends" usually air in Britain months after they are broadcast stateside. For impatient fans, the Internet offers bootleg, advertisement-free programmes that can be downloaded in a few hours over a high-speed connection.
Episodes of the espionage drama "24" show up on the popular file-trading network BitTorrent within minutes after they air in the US, according to Envisional, and a typical episode is downloaded by about 100,000 users.
The company said that "24" is the most pirated show online, with "The Simpsons," "The OC" and a host of sci-fi programmes including "Stargate SG-1" and "Enterprise" also popular.
Sky and other broadcasters such as Channel 4, which air large blocks of US shows, say they are monitoring the growing popularity of online TV downloads.
If the situation worsens, it may result in lower prices paid by broadcasters for shows such as "Joey", which went to Channel Five after an intense bidding war.
For the moment no one in the UK television sector will admit to losing any sleep over TV downloads.
"Unless you're a pretty big cybergeek, people are generally happy to watch it on TV," said an executive at one UK broadcaster who asked to remain anonymous.
Hollywood is not standing idly by. Fearful of a repeat of the rampant downloading that crippled the music industry, the Motion Picture Association of America has forced the closure of several sites that provide the links needed to download movies and television shows.
If that doesn't work, there is always the threat of lawsuits. When the MPAA shut down a site called LokiTorrent last week, they seized reams of data including logs of user data that could enable legal action against individual users.
"I'm not sure if the MPAA are going to follow that route," Price said. "The MPAA have found a very worthwhile technique, which is to go after the tracker sites and shut those down, which means the users don't have anywhere to go to get what they need."
But there is little evidence that Hollywood's counteroffensive crackdown has had any effect, according to Web analysis firm CacheLogic, which estimates that BitTorrent accounts for a staggering one-third of all Internet traffic.
"We've seen very little change, and in some cases we've actually seen an increase," said CacheLogic Chief Technology Officer Andrew Parker. "The MPAA has had no impact."