Wellington: New Zealand's ambitious firearm amnesty ends on Friday with questions over its success, as critics say the police only managed to collect about a third of the weapons that were outlawed after the Christchurch massacre.

Prime Minister Jacinda Ardern banned semi-automatic weapons and launched a gun amnesty and buyback scheme after a suspected white supremacist gunned down 51 Muslims in two mosques in March.

NZ acting police superintendent Mike McIlraith shows MPs in Wellington an AR-15 style rifle similar to one of the weapons a gunman used to slaughter 51 people at two Christchurch mosques in March. Credit:AP

More than 56,346 prohibited guns have been removed from circulation so far, within the range estimated by consultancy KPMG in an independent report, Police Minister Stuart Nash said in a statement.

"However police have consistently warned the problem is, we just don't know exactly how many guns are out in the community," Nash said.