Beneficiaries who fail drug tests could have their benefits cut off, under new National Party policy announced today.

The policy adds to the recently released plans to replace the current welfare system with three new benefits and force more people into work, including mothers who have additional children while on a benefit.

Today, National leader John Key said beneficiaries on the Jobseeker benefit who did not apply for a job because they were asked to take a drug test, or who failed a pre-employment drug test would face having their benefit cancelled.

Those evading police warrants would also have their benefit cancelled.

"Taxpayers should not be paying criminals to evade the law...we believe in a welfare system which is fair for to those who use it, but is also fair on taxpayers who fund it."

National would also allow Work and Income to match data with other agencies to catch people who were fraudulently claiming a benefit, Key said.

Similar matching this year found 6-12 per cent of people were receiving benefit payments they were not entitled to, he said.

"We will beef up authorities' investigative power, funding a new team of fraud specialists to hone in on reducing abuse across the welfare system."

And they would review the Social Security Act, particularly the rules around relationship fraud, to make it easier to prosecute people.

The changes were aimed at tightening up on those who were abusing the system, Key said.

"There is a small number who see welfare as a free ride on the taxpayer, and there are those who are facing a future of life-time welfare dependency."

National would be "hands-on" with helping people into work, he said.

Social Development spokeswoman Paula Bennett said National was getting tough on those who abused or exploited the system.

"We'll sanction beneficiaries if their recreational drug use gets in the way of a job, we'll cancel benefits for criminals on the run from Police and a new team of fraud specialists will focus on catching benefit cheats."

National recently announced there would be a part-time work expectation for sole parents whose youngest was over 5-years-old and those whose youngest child was over 14 would be expected to work full-time.

Other changes included a move to an investment based approach which would tailor support to beneficiaries based on their likelihood of becoming a long-term welfare dependent.

Expectations would be set on what people could do and people would be individually listed as being able to work part-time, full-time or be temporarily exempt.

The policy changes are in response to the Welfare Working Group's report.