An Auckland fast food restaurant worker says they were asked to effectively continue working after clocking out.

Photo: Supplied

A screenshot showed a message was sent in a WhatsApp group chat named Burger King Queen Street Manager Group last week, which appeared to say a staffer stayed after clocking out, and "if she can do it we can do that as well".

A worker at the store by Victoria Street, who didn't want to be identified, said she believed the manager who sent the message was encouraging everyone to work for free after their rostered shift was finished.

"The screenshot ended up saying if this person can clock out and then continue doing work, you should do it as well, and I found that very discouraging. It's saying clock out and finish work for free. No, that's not us," the worker said.

"I will get paid for whatever amount of work I do. If they're expecting me to work for free, sorry, I'm not going to do that. I will just finish my shift and leave."

The worker said she flagged it with the store management last week, emailing the screenshot to her area manager, her restaurant manager and the Unite union, but hadn't seen anything been done.

She said she was removed from the group chat shortly after she complained and believed the group has been disbanded.

Mike Treen from the Unite union said they have had a collective agreement with Burger King for more than a decade.

"That's not an acceptable request. That's an unlawful request because it's asking people to clock out and continue working. This is a constant problem we've had with fast food companies over the years," he said.

Employment lawyer Peter Cullen said an employer could ask staff to continue working after their shift finished by mutual agreement and the staff should get paid.

"If on the other hand, the employer wants people to work for nothing after they've clocked off, that's clearly illegal. They can take a personal grievance and claim the lost wages," he said.

Burger King head of marketing Jake Shand said in a statement that it had conducted an internal investigation.

"The restaurant manager has sent out an email to motivate the staff and the email was taken out of context. We are confident the Burger King manager has not asked the staff to work without pay and this was a miscommunication," he said.

"We have refreshed the management team with the policy on staffing and would like to reiterate that Burger King does not ask people to work without pay."