The final methodology for the assessment of council submissions on amalgamations has clouded the Fit for the Future process.
The Independent Pricing and Regulatory Tribunal released the details, which are the key to the future of Rockdale, Kogarah and Hurstville councils.
Opposition local government spokesman Peter Primrose said the methodology was "as clear as mud" and the process should be delayed.
Urban Taskforce chief executive Chris Johnson said the methodology was "good news" because there would be more flexibility.
Greens spokesman on local government David Shoebridge said the tribunal had "effectively rubber-stamped the government's forced amalgamation agenda".
Tribunal chairman Peter Boxall said they would take "a holistic approach" and would consider alternatives to mergers if councils could demonstrate they would deliver benefits to their residents that were at least as good as those envisaged by amalgamations recommended in 2013 after an inquiry by an independent panel.
Dr Boxall said it "puts the onus on councils to demonstrate how their proposals meet the criteria".
"There is no one-size-fits-all measure or universal minimum population size in assessing a council's scale, beyond the options provided by the Independent Local Government Review Panel in 2013.
"We are interested in how high-capacity councils are able to deliver quality services and infrastructure while keeping rates and charges affordable, and representing the diverse needs of their communities.
"Similarly, there is no overall pass or fail mark for the other criteria of sustainability, effectiveness and efficiency.
"What we are interested in is an overall assessment of a council's proposal.
Councils have to submit their proposals by Tuesday, June 30.
View the final methodology: ipart.nsw.gov.au