A Sydney council is determining development applications for new houses in just four days after introducing the planning equivalent of an express checkout lane.

Liverpool is trialling a new assessment process that aims to fast-track the construction of tens of thousands of new houses in major land release areas.

The city, which is set to become home to Sydney's second airport and is positioning itself as the "capital of south west Sydney", hopes the process will free up planning staff to focus on bigger and more complex proposals.

The process is  targeted at experienced developers who have lodged applications with the council previously and have an understanding of planning regulations.

They submit their plans through an online portal that sets out clear criteria for the development.

The council's customer service staff check the submission to ensure there are no omissions before the application is passed on to senior planning staff for determination.

Mayor Ned Mannoun said 60 development applications in new-release areas Elizabeth Hills and Edmondson Park had been determined within an average of four days. The process aims to have a 10-day turnaround.

Cr Mannoun said it puts the onus on developers to submit high-quality applications. It would, he said, save home buyers money by increasing supply and reducing planning costs.

​Liverpool Council had one of the longest average development application processing times in 2013-14.  According to Office of Local Government figures, it took the council an average of 104 days.

"We are one of the fastest-growing cities in the state and the home of Sydney's second international airport," Cr Mannoun said.

"Liverpool is set to accommodate more than 320,000 people by 2036. FastTrack is part of our strategy to meet the needs generated by that growth."

The fast-track process is being trialled at the moment and is open only to approved users and applications for houses in new estates.

It will later be extended to mum-and-dad builders and then possibly rolled out to other residential, commercial and industrial developments such as small subdivisions, secondary dwellings and carports.

More than 27,000 dwellings are planned for new-release areas in the Liverpool local government area during the next two decades. More than 17,000 are planned for Austral and Leppington North alone.

A council spokeswoman said the process would apply only to "low-risk" developments that would not usually require public consultation. The public would be able to view applications and supporting plans online at all times.

Local Government NSW president Keith Rhoades​ welcomed Liverpool's new process but said councils had to ensure they also stood "firm against greedy property developers".

"The trick lies in delivering this protection from inappropriate development without slowing down standard residential renovations and construction and other low-risk developments with red tape," Cr  Rhoades said.

Associate Professor Roberta Ryan, director of the Australian Centre of Excellence for Local Government and UTS Centre for Local Government, said an increasing number of councils was introducing streamlined assessment options.

The most important decision, Associate Professor Ryan said, was forming the criteria that determined what developments could be fast-tracked.

"Councils need to make sure that they are clear about what the things are that matter most to people locally," she said. "I would be surprised if most councils in NSW weren't looking at fast-track processes."