Justice reform struck down by NZ First

Labour's hopes of reforming the justice system by repealing Three Strikes legislation have been halted in their tracks by New Zealand First.

A proposal to repeal the controversial legislation will not be going to Cabinet on Monday.

"I acknowledge New Zealand First has concerns about the Three Strikes repeal," Justice Minister Andrew Little said.

"The strength of this coalition is that change only occurs with the support of all three parties."

In late May, Mr Little told Newshub repeal of the three strikes law would go before Cabinet in two weeks' time.

The three strikes law was passed under by the National-led Government in 2010. It means a person who is given a third strike can be sentenced to maximum prison time without parole. Thirty-eight crimes are listed as strike offences.

Mr Little said criminal justice reforms are still happening, but will be proposed by an advisory panel that is yet to be appointed.

"There is failure in the system that we have to address," Mr Little told media on Monday.

"[New Zealand First] are not prepared to accept our burgeoning prison population."

"They want to look at a total, well-balanced reform."

While Labour and the Greens campaigned on reforming the criminal justice system, NZ First has long taken a more conservative stance on crime.

The Opposition is calling the announcement an embarrassing back down.

"It's policy on the hoof and shows why Labour is so reluctant to make decisions and is instead sending everything to working groups - 122 and counting," National leader Simon Bridges said in a statement.

"When they do try and make a decision they make a mess instead."

In a week or so, NZ First leader Winston Peters will become acting Prime Minister. He's due to take up the role for six weeks after the Prime Minister gives birth.