WELLINGTON - A national memorial service to mark the "terrible loss of life" in the New Zealand Christchurch earthquake will be held on March 18, with Cantabrians to get the day off to attend.

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New Zealand Prime Minister John Key on Monday afternoon announced the service would be held at North Hagley Park in Christchurch at 12:45 pm.

"The service will allow people the chance to reflect on the terrible loss of life suffered as a result of the  earthquake and the huge impact it has had on our second-largest city," he told the post-Cabinet press conference.

"This is an opportunity for Christchurch to mourn together. It will also be a chance to celebrate the lives of those who have been lost," he said.

The New Zealand government would introduce legislation to make the date a provincial public holiday in Canterbury so local people could attend if they wished.

Two minutes' silence would be observed from 12:51 pm, the time the deadly magnitude 6.3 quake struck on Feb 22.

Key said the service would be "a beginning, not an end".

"While we will never forget those who have been lost, we must now focus that indomitable Canterbury spirit on the future."

The service was being organised by the Christchurch City Council and the Visits and Ceremonial Office, with wide consultation from the community and families.

Meanwhile, flags on government buildings would be raised at half-mast from 12.51pm on Tuesday to mark the exact time two weeks ago quake struck.