The Government has revealed the list of jobs and services deemed "essential" and, therefore, are not required to be in lockdown for the next four weeks.

The list includes border agencies, media, people in building and construction, courts staff and bank workers.

Some healthcare professionals are considered essential, as are people who work in public safety and local and national Government.

According to the Ministry of Business, Innovation and Employment (MBIE) essential businesses are those that support people and provide the necessities of life for everyone in New Zealand.

This means food, medicine, healthcare, energy, fuel, waste-removal, internet and financial support will continue to be available, MBIE said.

This list may, however, evolve over time.

These businesses will continue working but will put in place alternative ways of working to keep employees safe, including shift-based working, staggered meal breaks, flexible leave arrangements and physical distancing.

Earlier this afternoon, Prime Minister Jacinda Ardern moved New Zealand up to alert level 3 on the Covid-19 alert system.

That will be moved up to alert level 4 at 11.59pm on Wednesday night.

That means all non-essential businesses and services must shut their doors within the next 48 hours.

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Speaking to media, Ardern said essential services included supermarkets, banks, GPs, pharmacies, service stations, couriers and other important frontline service providers.

"I understand that self-isolation is a daunting prospect," Ardern said.

Public transport will only be open to those working in essential services, for medical reasons, or to move essential goods – including ferry services between the North and South Island.

BusinessNZ chief executive Kirk Hope said although businesses are required to close, it is reassuring that wage subsidies have been extended and that further work is underway on employee and business support.

What are essential businesses?

Accommodation:

• Accommodation services for essential workers and people who need to be isolated/quarantined

Border:

• Customs New Zealand, Immigration New Zealand and the Ministry for Primary Industries

Building and construction:

• Building and construction related to essential services, critical infrastructure, or immediately needed to maintain human health and safety at home/work

Courts, tribunals and the justice system:

• Courts of New Zealand and tribunals

• Critical Crown entities (eg Electoral Commission)

Fast-moving consumer goods:

• Businesses involved in the supply, delivery, distribution and sale of food, beverages and other key consumer goods (but not take-away shops)

Education:

• Schools and educational facilities (e.g. early childhood centres)

Financial services:

• Banks, insurers and other financial institutions

Health:

• Hospitals, primary care clinics, pharmacies, medical laboratories, care facilities

• Ambulance services

• Mortuary services

Local and national government:

• Any entity involved in Covid-19 response or that has Civil Defence/emergency management functions

• Key public services

Primary industries, including food and beverage production and processing:

• Packaging, production and processing of food and beverage products

• Food safety and verification, inspection or associated laboratory services, food safety and biosecurity functions

• Veterinary and animal health/welfare services

Public safety and national security:

• Emergency services

• Security and intelligence services

• Justice system

• Public safety and national security roles

Science:

• Any entity (including research organisations) involved in Covid-19 response, hazard monitoring, resilience, diagnostics for essential services

Social services:

• Welfare and social services, including NGOs, which meet immediate needs (further guidance will be provided)

Transport and logistics:

• Transport services

• New Zealand Post and courier services

• Any small passenger service vehicle driver – including taxis and ride-share services

Utilities and communications, including supply chains:

• Electricity, gas, water, waste, fuel, telecommunication services, internet providers and media