According to the Guardian newspaper, South Australia premier Jay Weatherill was pushing for a detailed look at other options, as well as the NEG, including the CET proposal by the nation's chief scientist Alan Finkel.
Australia's renewables trade body, the Clean Energy Council (CEC), said the government must address the concerns of the industry about whether the NEG can deliver the levels of clean capacity required to meet international targets.
"The clean energy industry will only support the NEG policy if it is designed and implemented in a way that ensures strong and sustained investment in renewable energy and energy storage," said CEC chief executive Kane Thornton.
"A lot of analysis and work is now required to fill in the detail necessary to fully assess the policy and its potential. This will determine whether it is capable of delivering this new investment and able to secure support from the clean energy sector," Thornton added.
The CEC also said it was worried the NEG would stifle innovation in new technologies or business models in Australia.
Australia's prime minister Malcolm Turnbull introduced the NEG in October.
The technology-neutral system removes support or tax, "creating a level playing field for all energy sources".
"The guarantee is made up of two parts that together will require energy retailers and some large users across the national electricity market to deliver reliable and lower emissions energy generation each year," the government said in a statement last month.
The two parts of the new arrangement include a "reliability guarantee" to ensure the correct level of "dispatchable energy... such as coal, gas, pumped hydro and batteries". The Australian Energy Market Commission and the Australian Energy Market Operator will set the level.
The second promise is an "emissions guarantee" to "contribute to Australia's international commitments".