An Australian undercover investigation firm has been inundated with applications from men applying for work as undercover operatives in brothel stings.

The investigations are funded by local councils who hire the firm to send an undercover investigator to a brothel to have sex with the sex workers in an attempt to gather enough evidence to convince judges to close down the illegal brothels, according to the Sydney Morning Herald.

Lyonswood Investigations last week revealed publicly they are looking for new recruits to undertake the investigations.

"It is evident from the responses that everyone has a different idea of what is needed to succeed in the job," Lachlan Jarvis, managing director of Lyonswood Investigations, said.

"One applicant wrote that he had had sexual contact with females of at least 83 different nationalities.”

The post was previously advertised in 2011 and Lyonswood received applications from around the globe. Just one man was deemed suitable however, having a private investigator’s license and good spoken English. The man was also willing to take his findings public in court if it was required.

The Sun Herald interviewed the current investigator and Fred Allen (an assumed name), told the paper he had been hired by local councils roughly 60 times to investigate brothels. The councils paid Allen to have sex and covered his expenses and transport.

"Never in a million years would I have imagined a job like this existed, let alone me doing it," the 60-year-old told the Sydney Morning Herald.

"It's a strange world for sure.

"I had never been to a brothel in my life so I was feeling quite nervous and apprehensive," Allen said.

"I didn't know what to expect. I reminded myself that this was a legal job exposing illegal activities. As far as first days at work go, I enjoyed myself."

"The drill is always the same," Allen added.

"An email arrives in my inbox providing the name, address and description of the premises. I then head in, get the information required and file a written report to the office, which is forwarded to the council."

A local council representative told the Sydney Morning Herald that they realised this is an extreme measure, but felt it was their last resort.

"It is an extraordinary process of evidence gathering," said the council's acting general manager Greg Woodhams.

"To use ratepayers funds for this exercise seems ridiculous. We don't like doing it, there would be a section of our community that disapproves of it ... but, until the system changes, we have no choice. We need to produce conclusive evidence."