Broadband firms will no longer be able to advertise their fast net services based on the speeds just a few customers get, from May next year.
Currently ISPs are allowed to use headline speeds that only 10% of customers will actually receive.
In future, adverts must be based on what is available to at least half of customers at peak times.
It follows research that suggested broadband advertising can be misleading for consumers.
The Advertising Standards Authority (ASA) looked into consumers' understanding of broadband speed claims and found that many were confused by headline speeds that they would never actually get in their own homes.