The competition watchdog says it is time for Sydney Airport to clean up its act after it delivered another scathing report showing customer satisfaction is the worst in the country.

The Australian Competition and Consumer Commission (ACCC) annual report uses surveys with passengers and airlines about the quality of service they received.

It raises concerns about monopoly pricing at Sydney and Melbourne Airports and cites problems with Sydney's international terminal, despite recent upgrades.

"At Sydney Airport, the airlines have identified unsatisfactory levels of service over several years, particularly at the international terminal," the ACCC said.

"There appears to have been no improvements to some services that the airlines rely on-such as the number of check-in desks."

But the report shows that Sydney Airport has the highest aeronautical profit margins, with a 2.9 per cent increase in revenue per passenger in 2009/10.

Short-term car parking is also the most expensive in the country, although the ACCC singled out Melbourne Airport for criticism over its parking arrangements.

Sydney Airport has undertaken its own research through Melbourne University and says the methods used to collect the data in the Commisson's report are flawed.

ACCC chairman Graeme Samuel says airport management should spend more time speaking to its customers.

"I would be less interested in what two academics at Melbourne University have to say about a report from the ACCC, I would be asking the airlines what is the problem," he said.

Sydney Airport management has not made itself available for an interview with the ABC.