Former staff at a cafe in Melbourne's north say they were underpaid by at least $5 an hour, and when they tried to discuss their wages with the owners their shifts were cancelled indefinitely.

Barry, on Northcote's upmarket Westgarth shopping strip, is owned by brother and sister Steve and Anne Petroulias.

Anna Langford said she and another worker had their shifts cancelled on Friday night after she sent the owners an email on behalf of nine staff asking to be paid the award rate.

Her payslip, seen by the ABC, shows an hourly rate of $18 for shifts including weekends.

Under the award, her minimum rate should have been $24.41 for weekday shifts, and $29.30 for weekends.

Staff were told they were not able to meet with management as a group. ( Supplied: Anna Langford )

Ms Langford said when she and other staff at Barry discovered the discrepancy, they approached the owners to discuss it as a group — a request that was rejected.

After that, she said, the owners approached the staff individually.

"When we were on shift they started to interrogate us, asking questions like 'who's the ringleader?'" she said.

Ms Langford said she sent a text message on April 7, again requesting a group meeting. That request was rejected once again.

In a text message to Ms Langford, Mr Petroulias told her: "Everyone can talk to me separately. It's the only way we can talk."

When asked why they could not meet as group, he replied: "Each one is a separate agreement. We can discuss separately."

At that point, Ms Langford said she and her fellow employees sought outside advice.

"We saw that we weren't going to get anywhere, so we got in touch with the Young Workers Centre and told them what was going on," Ms Langford said.

"They helped us draft an email to our bosses, signed by nine of us."

That email was sent on Friday afternoon. Mr Petroulias responded in an email later that evening.

"Hi Anna, Just to let you know that you and the other staff agreed each and every one of you the rate that you would be paid. "On top of that you all had free meals free unlimited coffees, and paid during your meal break. You came and went when ever you felt like and you begged us to come back after seven months away. "On top of that you asked us to employ your sister as well. If you weren't satisfied with your pay why all that. "All of you had previous experience, had worked in other cafes and you knew what the rates were."

Minutes later she received a text message from Ms Petroulias.

"Hi Anna. I just want to let you know that your shift for tomorrow has been canceled (sic). We let you know if we need you again. Thank you," it said.

Anna Langford was told her shifts had been cancelled via text. ( Supplied: Anna Langford )

Ms Langford said two other workers who signed the letter also lost their shifts.

Mr Petroulias said the shifts were cancelled because the cafe had too many staff, and that they were employed on a casual basis.

"They are casuals, they come whenever they went to, six months later, one will take a holiday. That's how casual is," he said.

Hannah Paletu'a resigned after receiving a text message saying her shifts had been cancelled. She does not accept the claim that the cafe was overstaffed.

She said during her time at Barry, she never saw anyone's shifts cancelled.

"We were always short-staffed," she said.

Ms Langford said she was stunned at the owners' reaction.

"We started off reasonably requesting a meeting — we didn't even mention backpay — but they've reacted really badly and just shut us down.

"This is the most successful cafe in the neighbourhood, and they're underpaying their staff by 25 per cent.

"All we asked for was the minimum award rate."

Mr Petroulias told the ABC he did not know he was underpaying his workers.

"I had a look on Google, and it said the average rate was $15 to $17 an hour, or something like that. And I was under the impression that $18 was the minimum rate," he said.

"Now that I've checked it, it's $18.51 or something."

The minimum hourly rate for full-time staff is $18.51, but for casual staff like Ms Langford the rate is $23.51.

A document Barry Cafe owners presented to staff to formalise their verbal employment agreement. ( Supplied: Anna Langford )

When this was pointed out, Mr Petroulias told the ABC: "If there is a mistake, I will correct it."

"I presumed that when they accepted the job, they were happy with what they were getting."

Mr Petroulias said that staff were provided with meals and coffee during their shifts, and that they were paid for their break of around 20 minutes on an eight-hour shift.

Ms Langford said the breaks were too short, especially on busy weekend shifts.

Staff, union members hold protest

Former staff and members of United Voice staged a protest at the cafe during lunch. ( ABC News: Jessica Longbottom )

Staff and United Voice union members protested outside the cafe today.

Customer Bec McNair and her friend were enjoying lunch when the protestors descended around them, making it near impossible to talk.

Despite the inconvenience, she said she supported the workers.

"I think good on them, and they should be entitled to a liveable wage and paid penalty rates and given breaks and not be paid in food," she said.

"I feel quite guilty sitting here amongst it all unsuspectingly, and I probably won't be coming back."

The Melbourne hospitality industry is under the microscope over pay and conditions.

Earlier this month, the ABC reported on allegations that exclusive restaurant Vue de monde required staff to work more than 20 hours a week in underpaid overtime.

The Fair Work Ombudsman is now investigating those claims, and is already investigating the Lucas Group, which owns the popular city eatery Chin Chin.

Barry cafe serves food and coffee on High Street in Northcote. ( Barry Coffee and Food )

Jess Walsh is the Victorian secretary of the hospitality union United Voice, which is mounting a campaign against underpayment in the industry.

"The way Barry Cafe has behaved could not be further away from the ethos of this community," she said.

"We will be coming out in force to stand with these workers to send a strong message to this cafe and venues across the state that we are not going to put up with this kind of treatment of hospitality workers any longer."