Tony Abbott has pared back the money available to his “green army”, recommitting to the 2010 election policy but saying it will now take five years for its “troops” to grow to the promised 15,000.

In 2010 Abbott’s green army – a voluntary program for 17-to-24 year olds to do practical environmental work – was allocated $400 million over four years. The 2013 version has $300 million to spend.

In both 2010 and 2013 the program began with a $50 million allocation. In 2010, that was estimated to be enough to pay for 4000 six-month training places, or 2000 army recruits at any one time. In 2013, after increases in the national training wage, the starting numbers in the army would have to be fewer than 2000.

The Coalition has not provided a detailed year-by-year cost breakdown for the 2013 version of the green army. It says it will still build to a 15,000 strong workforce, but this will now take five years. In the first four years no more than the new allocation of $300 million will be available. It says that will be enough for 1,500 projects.

Announcing the policy yesterday, the opposition leader said one of the first green army projects would be along the Georges River in Sydney.

Army recruits can be school leavers, students on a gap year, or young unemployed for whom it can act as an alternative work for the dole program. It will be administered by the environment department and projects will be chosen for their environmental benefit, contribution to the local community and capacity to provide the participants with training in specific skills.

As examples of possible projects, the coalition policy paper cites weed eradication, construction of sea walls, rehabilitating river banks and restoring walking tracks.

Abbott said the army “complements” the coalition’s “direct action” approach to climate change.

“At the same time as improving the local environment, the green army will foster teamwork, local ownership and community spirit in our young people,” he said.