Adulttoymegastore spokeswoman Janelle Cheesman says the survey results show how common "workplace relations" are in New Zealand.
"The fact that one in five New Zealanders have had sex with someone from work at least once in their lifetime shows how commonplace it is.
"Many people spend 40 hours a week with their work colleagues, so it's likely that romantic connections could form over this time," Ms Cheesman explained.
Whangarei employment advocate David Flaws said he practised in both Whangarei and Auckland and hadn't noticed a higher concentration of workplace sexual harassment complaints in Northland.
"First off, let's think about the differences between Northland and Auckland, and I practise in both places. I'd have to say that in relation to sexual matters I haven't noticed any difference."
If someone is dealing with unsolicited flirtation at work, Mr Flaws said, the person should tell the flirter that the behaviour isn't welcome and tell them they are offended by what they have said or done.
If the behaviour is repeated, it would then become an employment issue.
The person who is being repeatedly flirted with or harassed should approach their boss and tell them about the behaviour and urge them to take action so the person can feel safe at work.
"The onus is on the employer to provide a safe workplace," Mr Flaws said.
"Sexual harassment is forbidden and comes under both the employment relations act and constitutes an unfair disadvantage."
Everyone has a right to feel safe at work, Mr Flaws said.