Garth McVicar, the head of New Zealand's victim lobby group, says crime will increase if gay and lesbian couples are allowed to marry.

Lawmakers are currently debating a bill which would legalize gay marriage in the nation.

McVicar, head of the Sensible Sentencing Trust, submitted to Parliament that allowing such unions would have a devastating effect on society, leading to an escalation of child abuse and domestic violence.

“The marriage amendment bill will not benefit society at all and will ultimately have detremetal [sic] effect on crime at all levels,” McVicar's written testimony reads.

McVicar's submission is one of more than 20,000 received by a select committee considering the measure.

Green MP Kevin Hague told Fairfax that the submission was the only one he'd seen linking marriage equality to crime.

“Although it echoes a number of submissions that say marriage has been the same way for a long time and that if you tamper with it there will be lots of unforeseen circumstances,” he said.

McVicar's comments drew this response on Twitter from Labour MP Grant Robertson: “I was sold this marriage equality thing on the grounds that it would reduce crime – fashion crime that is.”