An official from the Department of Social Services has conceded there is no direct evidence to suggest forcing people under the age of 25 to wait a month to access the dole will prompt them to get jobs, describing it as a "decision of Government".

The measure, introduced in the Budget, was seen as a backdown from the Federal Government's previous plans to make young people wait six months to access unemployment benefits.

That measure was blocked by the Senate.

In questioning before a Senate committee, department officials cited the New Zealand approach — which involves young people completing a number of activities before they are eligible for benefits.

Under questioning from Greens senator Rachel Siewert, the department's Cath Halbert conceded the New Zealand system could not be compared to what was proposed in Australia.

"What examples, other examples beyond New Zealand, have you got that denying people income support for that period of time is going to be an activation for them?" Senator Siewert asked.

"It was a decision of Government, Senator, to apply the four-week waiting period and that was after, I believe, extensive consultation on the previous year's budget measure, which was a six-month waiting period and following that consultation the Government has decided to apply a four-week waiting period," Ms Halbert replied.

"Do I interpret what you're saying that in fact you haven't got the evidence on a four-week waiting period, it was a decision by Government?" Senator Siewert said.

"Not directly, no," Ms Halbert replied.

Social groups including the Australian Council of Social Service and The Council for Single Mothers and their Children told the committee the measures were punitive, and vulnerable families would suffer.