The comments come after Shadow Home Secretary Yvette Cooper called for a 'buffer zone' around health centres where abortions take place, in order to protect women from abuse.
Yvette Cooper said a woman in Chester needed police to help get to her car as she left an abortion clinic.
Another woman in London reportedly confronted activists, telling to stop judging" those having abortions.
Robert Colquhoun, from 40 Days for Life, told Premier's News Hour: "Our organisation... has been organising peaceful and prayerful vigils outside abortion centres for the last four years in this country.
"I've personally organised 3000 hours of prayer vigils. I've never seen an incident where somebody has been harassed or intimidated.
"I think that [ban] would be a severe curtailment of free speech as something more... like Soviet Russia.
"In the United Kingdom we have freedom of speech very clearly in the very essence of our country.
"We've seen hundreds of women choose life for their babies as a result of our peaceful presence outside the abortion centres.
"That's not something that would happen if you had a 50-metre buffer zone outside... Many of those women would not be able to have an offer of an alternative under that situation."
Labour Leader Ed Miliband has said he has to "think about" about the proposal of buffer zones around abortion clinics.
