The government is being urged not to hand over youth employment services to private providers.

The Green Party says it's "a risky ideological experiment" that's been tried overseas and failed.

The proposal is part of wide-ranging welfare reforms the government is considering, and the Treasury has warned that private providers could exploit the system.

Documents obtained by Radio New Zealand under the Official Information Act show the Treasury told the government it would be difficult to audit and monitor the effectiveness of privately run employment programmes.

The services help young beneficiaries find work or set them up with training and the Treasury questioned the ability of private providers to do that.

It said numbers could be inflated and it would be hard to establish how many young people were actually involved.

Green's co-leader Metiria Turei says it was tried in Britain and was a disaster.

She's citing a House of Commons report that says private providers delivered poor results and under-estimated the difficulty of the task.

"Private provision of youth employment services is nothing less than corporate welfare which will feather the nests of the providers' executives and shareholders," she said on Thursday.

Social development minister Paula Bennett says the documents are from April last year and a lot of work has been done on the proposal since then.

"There are always risks associated with change but there's little chance of private providers cheating the system," she said.