The Commonwealth Bank analysts, Andre Fromyhr and Matt Crowe, assessed how long it would be before the airport was unable to handle more planes and passengers without building a new runway or terminal.

They concluded it could be soon after 2025, much earlier than the airport management's prediction of 2045.

''By our passenger forecasts, Sydney will reach 61 per cent more passenger volume in 2025,'' the analysts said.

''With no major investment, this would match Beijing [Airport's] current utilisation. Beijing is running at 99 per cent of its 'design capacity'.''

Their assessment is broadly in line with a joint federal and state study released in March last year, which predicted that Sydney Airport would be at capacity by about 2020.

The analysts' conclusion has added weight to calls for urgent action to be taken on choosing a site for a second airport in the Sydney basin.

The federal Transport Minister, Anthony Albanese, said the analysts' report ''confirms what our joint study with the NSW government said - that Sydney needs a second airport sooner rather than later''. The shadow federal treasurer, Joe Hockey, who has long backed a second airport, was unavailable for comment but tweeted early on Wednesday: ''Sydney int'l airport. The slowest and most clumsy passenger wait in the western world.'' A spokesman said Mr Hockey was on holiday and had been picking up family from the airport.

But Sydney Airport said the Commonwealth Bank analysts' conclusion was based on a ''flawed assessment'', and ignored the fact it constantly invested in boosting its capacity.

Also, it did not take into account the fact aviation was becoming more efficient, which had allowed the airport to boost passenger numbers by 40 per cent since 2000 with virtually no rise in aircraft movements, the spokeswoman said.

Although the Transport and Tourism Forum believes it would make sense to build an airport at Badgerys Creek, its chief executive, John Lee, said regulation was limiting Sydney Airport's ability to boost its capacity. ''There are other levers available to government to examine, like the [flight] movement cap,'' he said. ''It is like having a three-lane highway and only opening one-and-a-half during the peak hours.''

Sydney Business Chamber's executive director, Patricia Forsythe, agreed political constraints meant Sydney Airport was significantly underutilised. ''Its capacity to support Sydney for a long period of time would be enhanced if we were able to get a better utilisation of the airport,'' she said.

However, she reiterated the chamber's support for a second airport in western Sydney, which it believes should be located at Badgerys Creek.

A spokesman for Barry O'Farrell said the Premier's views on the airport were well known ''but ultimately this is an issue for the Commonwealth''. Mr O'Farrell, who has opposed a second airport in Sydney, has proposed increasing the cap on flights at the existing airport.

A study commissioned by Mr Albanese into an alternative site for an airport at Wilton, more than 80 kilometres from the city centre, is due to be released early this year.