Some New Zealand companies have fared badly in the public eye during the Covid-19 outbreak, new analysis shows.

Business consultancy Rutherford analysed around 1.1 million posts on Facebook, Twitter, Reddit and Instagram to get a snapshot of how New Zealanders were feeling about Covid-19.

The study included gauging New Zealanders' discussion of companies which played a key role in the response to Covid-19.

It showed that two companies, the Warehouse and Briscoes, were associated with negative comments on social media.

The study did not go into the reasons behind the public's perception of them. But the Warehouse faced a backlash after it wrongly claimed it was an essential service and would remain open during lockdown - a move which led to its shares surging 30 per cent before a trading halt when the Government said it had to shut.

"There was a bit of negative reaction around that," said Rutherford's head of insights and experimentation, Gregg Franco.

"And some of that perception has carried over to Briscoes, which is in the same industry."

Supermarket chains Countdown and New World and broadcaster TVNZ were seen in a positive light for their work during lockdown. Other companies which were viewed positively were Sky TV, online shopping company Mighty Ape and Les Mills.

Government departments were also included in the analysis, and all of them were seen negatively. Franco said this was not unusual, and it was important to look at government departments in relation to each other.

Police, the Ministry of Health, and ACC were doing relatively well, he said, while the Ministry of Social Development was viewed very negatively.

MSD has been under intense pressure because it has been swamped by people made jobless by Covid-19. Some people have complained of taking a week to get through on its phone lines.

The analysis also found that Covid-19 has dominated social media in New Zealand like no other event before it.

Discussion about the virus featured in 8.1 per cent of all social media conversations in this country since the outbreak began. While that did not appear to be a high figure, it completely dwarfed other comparable events in the past five years.

By comparison, the Kaikoura earthquake in 2016 took up 1.6 per cent of New Zealand social media conversations at the time, the Whakaari/White Island eruption 0.6 per cent, and the Christchurch mosque attacks last year 0.5 per cent.

The analysis also looked at how New Zealanders' emotions changed over time.

"What is interesting is that just before we went to level 4, there was a lot of talk of fear and uncertainty," Franco said.

"That peaked at the beginning and has been decreasing steadily over time."