Natalie Collins, a Christian who works for Spark, a domestic abuse prevention, made the comments after Jeremy Corbyn's suggestion that women-only train carriages could be introduced - to guard against attacks at night.
The frontrunner in the Labour leadership contest says he would hold a consultation on the idea if he is elected in September.
He has suggested a 24-hour hotline for women to report harassment as well as tougher rules for licence holders on reporting assaults on their premises.
Natalie Collins told Premier's News Hour: "I would suggest for many reasons it's very problematic.
"Actually what we need is a system where there's a zero tolerance policy on harassment, rather than putting women in a place where they can't be harassed.
"What we need is bystander interventions - where if somebody's sees harassment happening, they challenge it rather than turning a blind eye.
"It's where we train up police to really understand harassment, it's where we train up people who work on the transport system to know how do I support women and how do I ensure that we prevent these sort of behaviours happening."
She warned that this debate could distract from the real issue of harassment: "We end up with either people being very anti-women-only carriages or very pro-women-only carriages and what we don't get is a wider conversation about the very serious reality of male violence, and male abuse of women and men thinking they have the right to have access to women's bodies."
Listen to Premier's Marcus Jones speak to Natalie Collins here: