Premier Peter Beattie was today considering strengthening legislation to make all public servants gain approval from management for a second job after it was revealed a Gold Coast teacher was moonlighting as a prostitute.

While the woman had not acted illegally, Mr Beattie ordered an investigation into the woman in "the best interests of the students".

However, Queensland's Anti-Discrimination Commissioner Susan Booth said it was illegal to discriminate against a person on the basis of lawful sexual activity.

"I'd remind government that that is the law in Queensland and what teachers do in their own private time is very difficult to regulate," she said on ABC radio today.

"That would include both teachers who are working as lawful sex workers and teachers who may wish to attend a lawful brothel."

The Education Department asked the woman, who worked at a public school, to quit after discovering her second job about 15 months ago.

She was allowed to continue teaching but had since been placed on special leave with pay amid fresh allegations she had resumed working as a prostitute and had supplied alcohol to students on a trip.

The Government said there was no evidence to support claims she was again working as a prostitute.

Allegations about the supply of alcohol to students have been referred to the Crime and Misconduct Commission (CMC).

Mr Beattie said it was unreasonable to expect the teacher to continue both jobs.

"I don't believe the community standard is that if you're a school teacher, you should also be a sex worker," he said.

Queensland's opposition rubbished the plans to change the law, saying the matter was an issue of morality.