In the digital media age, declaring fake news has become the equivalent of crying wolf. Frequently, it is a slur hurled at journalists by those who do not like a story. Sometimes it is a real threat to informed discourse. It is disturbingly easy to propagate, and wields insidious power. This week, I learned just how damaging it can be.

I had just returned from an afternoon at the beach when a tweet with my name in it caught my eye. I recognised the image. It was one I had taken nearly three years ago at a pro-Syrian refugee rally while working as a reporter in Saskatchewan, Canada. In the original image, a woman wore an Amnesty International sign around her neck reading “My door is open for refugees”. But that’s not what this image said. The words had been edited to read “My legs are open for refugees”, in what looked like a Microsoft Paint chop-shop job by a 12-year-old, and it had been shared by none other than Nigel Farage. “What an insult to the victims of sexual abuse in Cologne and rape in Malmo. These people are sick,” he tweeted.

‘Nigel Farage’s words carry weight and they fly far, and when those words carry the wrong information it does a great disservice to all who read them.’ Photograph: Patrick Seeger/EPA

I had first seen this doctored image about a year ago. It was frustrating to see my work altered, taken out of context, and used to serve someone else’s agenda. It didn’t matter what that agenda was. It mattered that they were spreading false information. At the time, it was being shared by random people on Facebook. I saw them as internet trolls having a laugh, and thought it would be better to let it pass. To demand that it be taken down would draw attention and risk it spreading further.

It was frustrating to see my work altered, taken out of context, and used to serve someone else’s agenda

But on Sunday, it was different. It was a public figure, a current broadcaster, and a man who still has the ears and eyes of thousands of people daily. His words carry weight and they fly far, and when those words carry the wrong information it does a great disservice to all who read them. And Farage wasn’t alone. The image was shared by the actor James Woods, and by a Facebook group called, ironically enough, Stone Cold Truth.

By the time I was informed, Farage had already removed the tweet. In a follow-up, he did acknowledge the image was fake, but the damage was done. More than 1,000 people had retweeted the doctored image, many possibly believing it was real, wishing it was, or just liking how it meshed with their world view.

Farage also asked people, specifically those who support refugees, to “think hard about what is happening”. But as a reporter, I began to think hard as well. I thought about how in an era of instant information-sharing it is more important than ever that we verify what we are spreading and own up to our mistakes when we falter. This is especially true for those who exert some level of influence over others.

I hope Farage and others think hard about what is happening to the public discourse when fake news, whether intentionally or not, is being branded as true and shared by thousands. It doesn’t do our causes, the public or the woman in that photo any good.

• Lasia Kretzel is a Canadian photographer, reporter and broadcaster. She currently works as a digital reporter for NEWS 1130 in Vancouver