Winston Peters says a move to allow Sikhs to carry their ceremonial dagger would be unfair to others - including Maori who want to carry a taiaha.
National list MP Kanwaljit Singh Bakshi has a private member's bill in the ballot to allow a baptised Sikh person to carry a kirpan in public places and workplaces, without this being an offence.
And Prime Minister Bill English told a gathering in Auckland a week ago the Government, if re-elected, will change the law to allow the kirpan to be carried, according to the Politik website.
Former Prime Minister John Key in 2015 said the Government was considering exempting kirpans from civil aviation rules, to allow them to be carried onboard and not stowed with luggage.
Those comments came after seven Sikh cricket fans were barred from watching a Cricket World Cup match at Eden Park because they were wearing kirpans.
A kirpan is a small sword or dagger, worn in a sheath on a strap or belt.
In August, a Sikh man was removed from an Air New Zealand flight from Christchurch to Invercargill, after another passenger noticed his kirpan.
Despite those problems, Peters said changing the Crimes Act to allow Sikhs to carry the kirpan would be a rule to favour them over others.
"If Sikhs can do this as part of their customs, then what do we say to Maori who want to carry their traditional weapon, a taiaha, or perhaps a Hindu who wants to carry a trident, their traditional three-pronged spear.
"Perhaps it's time for a serious talk with the Sikh community to avoid people walking around with a dagger of cold hard steel."