By Jonathan Davies
Citizens Advice says broadband providers are misleading customers over the the real, long-term costs of a contract.
The charity said that costs like line rental and delivery fees, which are often not clearly shown in adverts, could add up to £20 a month on top of the advertised price.
In one case, Citizens Advice said customers would be paying £465 more than advertised over the course of a 12 month contract.
Gillian Guy, chief executive of Citizens Advice, said so-called 'teaser' rates make it confusing for consumers to gauge whether or not they are getting a good deal.
"Internet providers need to be upfront about broadband costs, ensuring adverts are transparent and people know what they are signing up to," she said.
"Some broadband firms are starting to accept that prices need to be clearer. Now the whole industry needs to up its game."
Nicholas Lansman, secretary general at IPSA, the trade body that represents broadband providers, said prices are "clearly presented".
He said: "It is important that customers look at the full terms of an offer when choosing a provider.
"Ofcom recently concluded that the UK has one of the most competitive broadband markets among major European economies, as the average price of a fixed broadband package has fallen by 40% and speeds have greatly increased."