Former prime minister Tony Abbott has slammed the federal government's plans to axe the Green Army environmental program, suggesting Malcolm Turnbull is caving in to the Greens.

Environment and Energy Minister Josh Frydenberg all but confirmed reports the $350 million program would be scrapped on Monday, as the government's Expenditure Review Committee ticks off on savings ahead of this month's budget update.

Established after Mr Abbott's 2013 election victory, the Green Army was designed to use the manpower of up to 15,000 unemployed young people, aged 17 to 24, for conservation projects in every state and territory.

Prime Minister Malcolm Turnbull said he wouldn't comment on the project's demise before the mid-year economic and fiscal outlook statement, due on December 19, while Green Army service providers were surprised by the reports.