Changes to online copyright law could make broadband "unaffordable" for thousands of people, a consumer group said.
The Government has announced internet service providers (ISPs) will pay 25% of the costs of any challenges against suspected online piracy.
Minister for Communications Ed Vaizey said the move would help protect the "creative industries" which lose out when content, including music, is shared online without being paid for.
But Robert Hammond, from Consumer Focus, said increased ISP costs could be passed on to customers.