NTL is unlikely to be the last operator to introduce restrictions on its users, according to analysts.
Earlier this week NTL told customers of its broadband service that they will be limited to 1GB of downloads per a day.
Download capping, already introduced in Europe, the US and Australia, will let operators plan future investment in networks and infrastructure, according to Michael Philpott, broadband analyst at Ovum.
"Operators are paying a heavy price to meet the back-haul demand that heavy users place on their networks," he explained.
"UK operators have been quietly talking about the possibility of capping or different tariffs for sometime.
"This means that the days of 'all you can eat' are gone and it wouldn't surprise me if more introduced capping."
Philpott said that, despite the promises of always-on and unlimited access, as the number of broadband users increases, operators need to know that the infrastructure can handle the traffic in order to protect mainstream users.
And as file-sharing in Europe is growing at such a phenomenal rate, broadband service providers are struggling to manage their networks, according to Jupiter Research.
NTL has claimed that it has no plans to introduce draconian penalties if heavy users exceed the new limits, although it would not rule out further restrictions in the future.
A spokeswoman said: "If a user downloads more than the 1GB over three days in a 14-day period, then we will call them to discuss this.
"We have no plans to cut their service, but if people then abuse the service we will look at the situation on a case by case basis.
"We are also compiling a list of what we call the 'power users' to see if we can develop a forum to discuss setting up new services."
Telecoms watchdog Oftel stressed that the NTL announcement should not affect consumer confidence in broadband services.
"This is a contractual matter and not an area for Oftel. But there is competition in the broadband market, so people can change to other providers," said a spokesman.
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