Darling Harbour restaurant Baia The Italian has been ordered to pay $15,000 in compensation for the unfair dismissal of an employee who complained about being allegedly underpaid.

In deciding the dismissal was harsh, unjust and unreasonable, Fair Work Commissioner Donna McKenna said the restaurant's conduct was "of the shabbiest type" in its use of its 457 visa-related "leverage concerning potential work-related sponsorship in the course of underpaying an employee".

The Fair Work Commission heard the French national Sebastien Mezino was told the restaurant in Cockle Bay was willing to offer visa sponsorship to dedicated employees.

Mr Mezino, who was employed with Baia from November 2015 until April 2017, told the Commission he sometimes worked more than 50 hours a week but was happy to do so because he wanted to prove to the company he was "worth their investment". He said the restaurant manager told him that depending on his performance he could expect a promotion to a manager's position with an offer of visa sponsorship.