Simon Bridges says National is committed to bringing back sanctions on beneficiaries to give them "more esteem and more of a purpose".
The Labour-NZ First coalition has removed, or is in the process of removing, many of the punishments introduced by the previous National-led Government after winning last year's election - such as docking payments to solo mothers who don't name the father of their baby.
The number of beneficiaries being sanctioned fell 22 percent in the last year, figures released to NZME last week showed. The biggest falls came in sanctions for failing to show for appointments and failing to prepare or participate in work. Work and Income staff have reportedly been encouraged to explore other options first, and any sanction now has to be signed off by a second person.
Mr Bridges told The AM Show on Monday National would "absolutely" reinstate sanctions if they win the next election.
"We need to be fair to taxpayers, hard-working taxpayers who deserve actually their money to be spent well, but also the beneficiaries who in terms of getting into a job, have a better life quality actually have more esteem and more of a purpose."
He said the aim wasn't to be "tough".
"It was about making sure we had expectations on beneficiaries that would lead to better lives for them. This Government's going soft in this area - it's a bit like crime, it won't work. It'll mean more beneficiaries, more people languishing on the dole queue, when we've actually got low unemployment in this country. It's a tragedy."
Last year, Newshub Nation revealed Ministry of Social Development reports addressed to then-minister Anne Tolley argued sanctions didn't work, and actually cause greater long-term welfare dependency.
International research has come to much the same conclusion. A five-year study in the UK recently concluded sanctions "do little to enhance people's motivation to prepare for, seek or enter paid work", the Guardian reported in May.
Unemployment has been on a downward trend since September 2012, in the wake of the global financial crisis. The last time it rose was in the December 2016 quarter, to 5.3 percent. It's presently 4.4 percent.
Before the election the Green Party vowed to scrap all sanctions. It backed down during coalition negotiations, accepting that only "excessive" sanctions would be removed.
National, on the other hand, promised to take away up to 100 percent of jobseekers' benefits if they failed to comply with requirements.
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