TOUGH new grooming measures have been introduced at the Immigration Department after some public servants tried to wear Ugg boots and even onesies to work.

Department secretary Mike Pezzullo​ told a Senate Estimates hearing that he was forced to make a determination as to whether onesies - a one-piece leisure suit - was appropriate workplace attire.

“I didn’t even know what a onesie was, and I was shown pictures of such garb,” he said.

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The committee heard that the guidelines were about “providing certainty” after some staff also appeared at work in jeans, thongs and Ugg boots.

Greens Senator Sarah Hanson-Young asked department heads whether they thought the guidelines were necessary or whether it was common sense.

“I couldn’t imagine that many people would be rocking up to work in Ugg boots?” Ms Hanson-Young said.

“You’d be surprised,” a departmental head told the committee.

The new code of conduct which came into force in March also prevents up to 8000 public servants within the department from working second jobs or using personal phones at work.