Labor leader Bill Shorten says the Morrison government's plan to use of carbon credits generated before 2020 to count towards Australia's Paris climate goal exploits a "technical loophole" - but one he won't rule out using if the ALP wins office in May.

Mr Shorten told media on Monday he was "taking advice" on whether the expected surplus of 367 million tonnes of carbon dioxide-equivalent generated during the current Kyoto Protocol period can be used for the 2021-2030 Paris accord decade.

Emissions plans remain hazy, with Labor not ruling out a plan to count Kyoto carbon credits against Australia's Paris climate target. Credit:AP

The Morrison government confirmed last week it intended to carry over the credits, effectively slashing the abatement effort by more than half the Paris abatement effort from 695 million tonnes to 328 million tonnes.

"[T]his government is relying on a technical loophole to do the heavy lifting because they don't have any other climate change policies," Mr Shorten said.