New Zealand bakery giant Couplands has shut down its South Island manufacturing plant as the coronavirus lockdown continues to bite.

Couplands said this afternoon that with the closure of its 25 stores nationwide it has become "unviable at this stage" to keep its South Island manufacturing plant and distribution operational.

However, its North Island manufacturing plant is still fully operational and producing bread for dairies and some supermarkets.

"To keep in line with the Government's request to keep food shopping to your local area, we will not be releasing a list of current stockists of our products," Couplands said in an update on its Facebook page today.

"We understand whilst this might be frustrating, we feel it is the most responsible route for us to undertake at this stage."

As one of the country's largest independently-owned bakery chains, it says it firmly believes it's an essential service - providing a basic food staple - but will continue to follow the rules as given.

Couplands bosses have spoken with Christchurch MP Gerry Brownlee who is lobbying on their behalf as they try to "get up and running as soon as possible".

"We are loving hearing your support for our products and company, and look forward to serving you again very soon. Keep safe New Zealand and thank you for your understanding."

The nationwide Covid-19 lockdown is having widespread ramifications across New Zealand industries.

• Covid19.govt.nz: The Government's official Covid-19 advisory website

Spending through Paymark dropped more than 70 per cent on the first day of lockdown, and remained at record low levels through the week to Sunday, March 29.

On the Monday and Tuesday ahead of the lockdown on March 26, however, spending was up about 50 per cent on the same time a year earlier. The increase was particularly up at liquor stores, hardware, homeware and recreational stores.