Unemployment and sickness beneficiaries will miss out on the main "carrot" offered in last month's package to get people off welfare into work - a higher allowable income before benefits are clawed back.

The increase in allowable income, from $80 to $100 a week, was promised in the National Party's 2008 election policy for all beneficiaries.

But the small print in last month's package, unnoticed at the time, says the increase will apply only to people on the domestic purposes, widows and invalids benefits and veterans pensions.

"People on unemployment benefit, sickness benefit and independent youth benefit will not have abatement thresholds increased," the Ministry of Social Development said.

"The aim for people on these benefits is a return to fulltime work as soon as possible."

Beneficiary Advocacy Federation spokeswoman Kay Brereton said the decision would mean a "double whammy" for people on the invalids benefit who are being bumped down to the sickness benefit by tighter enforcement of the work capability test.

Cabinet papers show that Social Development Minister Paula Bennett argued for the restriction to "avoid improving the incentives for people to work part-time for those people for whom fulltime work is the desired outcome".