The Fair Work Ombudsman has pounced on dozens of venues in some of Melbourne's most popular dining districts in the hopes of catching out dodgy businesses underpaying their workers.

Workplace inspectors this afternoon descended on Swanston Street and Lygon Street in Carlton, Sydney Road in Brunswick and St Georges Road in Fitzroy North.

More than 50 bars, cafes and restaurants were asked to produce records proving how much they paid their workers.

Sydney Road, in Melbourne, is one of the precincts receiving a surprise visit from the Fair Work Ombudsman. ( AAP: Julian Smith )

The ombudsman, Natalie James, said inspectors would be interviewing workers and their bosses.

"Many of us in Melbourne have eaten some excellent food on these streets and are familiar with these precincts," she said.

"The question for us is how sure are we that the workers who are preparing that food and carrying it to our tables are being paid correctly.

"We have received intelligence that suggests that there might be some practices going on in these precincts that aren't lawful."

Ms James said the ombudsman had received tip-offs that workers were being paid in cash and flat rates of pay.

"We always advise employees, keep your own records," she said.

"We often find workers have, when they suspect something is going wrong, kept quite meticulous records of their own. We can and we do use that in evidence in court, if it comes to that."

She said businesses had no excuse for shirking their workplace responsibilities.

"Just this month ... a court handed out penalties of over $600,000 to an operator at Sunshine fruit markets for underpaying an Afghani refugee, and so the penalties can be very serious," she said.

"So we advise employers, you need to check... make sure you're paying your workers correctly."