Changes to online copyright law could make broadband "unaffordable" for thousands of people, a consumer group said today.

The Government has announced internet service providers (ISPs) will pay 25% of the costs of any challenges against suspected on-line 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.

He said: "Consumers should not be picking up the tab for the enforcement of copyright laws that will benefit the music industry to the tune of millions.

"The previous government admitted any extra cost on ISPs may push up the cost of broadband, making it unaffordable for thousands of vulnerable consumers who need internet access to get vital services and cheaper deals."

The other 75% of the costs will be met by copyright holders under the proposals announced today.

The fee will pay for the initial notification of people who are believed to have infringed online copyright.

Mr Vaizey said: "The Digital Economy Act serves to reduce online copyright infringement through a fair and robust process and at the same time provides breathing space to develop better business models for consumers who buy music, films and books online.

"We expect the measures will benefit our creative economy by some £200 million per year and as rights holders are the main beneficiaries of the system, we believe our decision on costs is proportionate to everyone involved."

The measures will come into force in 2011.