Workplace Relations Minister Iain Lees-Galloway says if retail staff allegations are proved to be true, 12 of New Zealand's largest retailers are breaking the law.

Retailers accused of not paying staff overtime have been sent a strong word from the Government.

Workplace Relations Minister Iain Lees-Galloway said the retailers, outed by a union on Wednesday, must make sure they pay staff properly.

"My message to employers is make sure you know your obligations as employers," Lees-Galloway said.

SUPPLIED An Employment Court decision released on Friday ordered retailer Smiths City to pay staff for the meetings they turned up to without being paid for eight years.

"Make sure you're taking care of your staff."

READ MORE:

* Union releases list of employers allegedly making staff work overtime for free

* Smiths City case triggers hundreds of complaints on unpaid work

* Smiths City's unpaid meetings puts businesses on notice

First Union had received 1500 complaints from workers at more than a dozen of New Zealand's largest retailers since an Employment Court decision ruled retailer Smiths City to back pay staff.

MARION VAN DIJK/STUFF Briscoe Group admits it was not paying some staff for cashing up counters when stores closed.

Smiths City was found guilty of not paying for 15-minute sales meetings at the beginning of shifts for eight years.

The union released a list naming and shaming other offenders on Wednesday.

It included Kmart, Briscoe's, Rebel Sport, Countdown, Pak 'n Save, Cotton On, Farmers, Whitcoulls, The Warehouse, Warehouse Stationary, Noel Leeming and Harvey Norman.

MILANA RADOJCIC/SUPPLIED Cotton On Group did not respond when asked if it would investigate staff complaints about its pay practices.

More retailers complained about were yet to be named by the union.

Hundreds of the workers' complaints alleged they were not paid for time spent preparing a store before it opened and cleaning, or cashing up the till, after closing.

Lees-Galloway said if the allegations were true, "these employers are in breach of the law".

Senior management at Briscoe Group, owner of Briscoes, Rebel Sport and Living & Giving, investigated complaints laid against it on Wednesday.

After auditing all of its stores it found that some sales staff were not paid for the time they spent cashing up when a store closed because it was not included in their timesheet.

A Briscoe's spokesman said it was a company "error" and the staff affected would be back-paid.

Almost all of the other companies denied any wrongdoing.

The Warehouse Group, owner of The Warehouse, Warehouse Stationary, Noel Leeming and Torpedo7, said its sales staff were paid for every hour they worked.

Progressive Enterprises, which owns Countdown supermarkets, and its competitor Foodstuffs, which owns Pak 'n Save and New World, both said staff were paid for all time worked.

James Pascoe Group owns Farmers and Whitcoulls. Its director Kevin Turner said it was company policy for staff to be paid for meetings. He did not say if the same policy applied to cleaning or cashing up.

Australian conglomerate Wesfarmers, owner of Kmart, and Cotton On Group, owner of Cotton On, Cotton On Kids, Cotton On Body, rubi, Typo, Factorie and Supre, were all contacted for comment but did not provide a response.

Harvey Norman, owned by Australia's Harvey Norman Holdings, has been approached for comment.

First Union retail secretary Tali Williams said all the companies that were complained about were sent an email from the union asking them to investigate staff complaints.

Legal action could be taken against the companies if they refused to cooperate, she said.

Labour Inspectorate national manager Stu Lumsden said complaints it received had increased 15 per cent since the Smiths City ruling was released on Friday.

Inspectors would contact employers this week asking them to fix illegal practices and back pay owed wages, he said.

"Any employer who has been systematically exploiting their workers in this was, should, prepare for a knock on the door from the inspectorate."