Even those who chose a premium package including faster broadband and extra channels including Sky Sports would only pay £780 a year under a new deal.
Minister for Digital Margot James said: “It is outrageous for loyal customers to be penalised like this and I’d encourage them to always shop around for the best deal once their initial contract ends.
“We’ve strengthened Ofcom’s powers to better protect consumers, and will continue to work with Which? and others on a fairer and more transparent system that helps people save money.”
The findings follow concerns raised about loyalty penalties within the broadband, mobile phone, insurance and mortgage industries.
The Competition and Markets Authority recently made a series of recommendations to address loyalty penalties after finding that consumers were being overcharged by around £4 billion annually, with the less well-off and the elderly most likely to be overpaying.
Alex Neill, Which? managing director of home products and services, said: “Yet again we’ve found that loyalty doesn’t pay when it comes to your broadband and TV service.
People will choose their provider often because of a cheap introductory deal and then stay for the content offering.
“However, you shouldn’t accept getting a bad deal, there are potential savings to be made for those who take the time to haggle and even bigger savings for those who switch.”