CUSTOMERS of Telstra's BigPond have given Australia's largest internet service provider a resounding thumbs down, saying it costs too much, has poor levels of service and is not as fast as advertised.

The survey of 3870 internet subscribers by the consumer group Choice found customers of the smaller providers Westnet and Internode were the most satisfied with their level of service.

But in a worrying trend for the industry, overall levels of satisfaction have slumped from 41 per cent two years ago to just 29 per cent.

A Choice spokesman, Christopher Zinn, said the overall decline could be partly due to more people switching from dial-up internet to ADSL and paying more for the privilege.

In just two years dial-up usage has dropped from 47 per cent to 8 per cent of those surveyed while nearly two-thirds now used ADSL or updated versions of ADSL.

"Cost was the biggest issue right across the board, that was what people said. If you look at Westnet or Internode, some of them are priced more keenly and they are at the top of the satisfaction with cost factors," Mr Zinn said. "That's obviously where they find their niche in the market."

Only 10 per cent of BigPond users were very satisfied with what they paid for the service.

"That was down from last time [two years ago]," Mr Zinn said.

"They are also more likely to be hit with excess usage charges, so there was those kinds of issues with the costs that they pay and the conditions that they wear that caused this decline."

BigPond customers were also least satisfied with connection speeds versus what was advertised and had the most problems with billing. TPG, iPrimus and OptusNet had the next lowest overall satisfaction levels.

Ninety per cent of those surveyed had not changed their provider in the last year while more than a third chose their provider because they had phone and pay-TV accounts with it.

BigPond's corporate affairs manager, Craig Middleton, said the provider was not trying to compete on price and was offering a premium service.