The Government will repeal the "year and a day" law that was used as one of the reasons why police chose not to prosecute anyone over the collapse of the CTV building, which killed 115 people in the 2011 Christchurch earthquake.

Prime Minister Jacinda Ardern made the announcement during her post-Cabinet press conference today.

Section 162 of the Crimes Act says that no one is criminally responsible for the killing of another, unless the death takes place within a year and a day after the cause of death.

Crown Law cited the rule as an obstacle to prosecution in the CTV building case, where 115 people died when the building collapsed in the 2011 earthquake.

Police last year decided not to prosecute because they did not believe a prosecution would succeed.

Ardern met with the victims' families last month and said afterwards that she believed the rule had no place in New Zealand law.

She said today that Cabinet agreed to remove the rule today.

"I made an undertaking to the families of the CTV building collapse when I met them that changes needed to be made so that those whose actions lead to tragedies, can still be prosecuted no matter what length of time has elapsed," Ardern said.

"I know this won't help those families, but this law change will help ensure that those who face similarly tragic circumstances will not be prevented from seeing justice done.

She said the CTV building design occurred in 1986.

"This provision has already been abolished in most like-minded jurisdictions including the United Kingdom through the Law Reform (Year and a Day Rule) Act 1996, Ireland, Canada and most Australian states.

"It has also become obsolete because of medical advances that keep people alive for longer than a year and a day. This is the right thing to do so those who do break the law in these circumstances can no longer escape prosecution."