Psychotherapists have backed a petition calling for the Government to dump its social bonds plan.

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Under the plan, a non-government organisation would sign a contract with a private investor to deliver a service. An investor will see his money returned if the end result is favourable, while they will lose it if the outcome isn't successful.

The government is introducing the initiative to deliver employment services to people with mental health conditions in the first of four social bond announcements.

A petition against the move is being hosted by grassroots campaigning movement ActionStation, with the backing of the Association of Psychotherapists.

The Association's Chair of Public Issues, Kyle MacDonald said the government was trying an untested and experimental treatment approach.

"We're not necessarily against the idea that we need to help get more people back into work," said MacDonald. "But I guess the concern is that introducing private capital actually means the people are going to be pushed into work and that's what we would look to prevent."

As well as calling for an end to the policy, the petition also calls for the government to increase funding for mental health treatment as well as support.

MacDonald claimed they were worried it was the thin end of the wedge.

"That actually what the government's looking to do is sort-of privatisation by stealth," stated MacDonald, "and introducing more private funds into an area where we think, 'actually the government should be including government funding into mental health support services'."

MacDonald said the plan would impact some of the most vulnerable people in the country if implemented.