Canada’s Green party has admitted to manipulating a photograph on its website to make it seem as if the party leader was using a reusable plastic cup and metal straw instead of a disposable paper cup.

The image shows Elizabeth May, smiling and holding a plastic cup emblazoned with the Green party logo and with a metal straw inserted in its cover.

But the same photo had previously appeared on news websites and showed that May was holding a paper cup with no straw, the National Post reported.

Confronted with the clear discrepancy, May told reporters she was “completely shocked” that staff had edited the image without her approval.

“And I’m sorry for the staff person that did it. I don’t want to call them stupid on television, but there was nothing there to hide. So why Photoshop it? I have no idea.”

May denied that the manipulated image was meant to bolster her environment credentials, arguing that paper cups are compostable.

“It won’t surprise you to know I never take a plastic drinking water bottle, I carry my own mug, I carry my own utensils on airplanes so I never take a single-use plastic item,” May told reporters. “So it’s bizarre that the notion of fakery should stretch to someone who doesn’t fake anything.”

In recent months, plastics have become an environmental touchstone in Canadian politics, after the Liberal government pledged in June to ban single-use plastics, including disposable plates and utensils, by as early as 2021. Shortly afterwards, however, Justin Trudeau was photographed in a meeting with single-use items scattered on the table, and as a result, some politicians have become wary of images that could potentially undercut their environmental credentials.

May did, however, have advice for her team in the event they chose to manipulate another image: “If they’re going to Photoshop, couldn’t they do something with my face and make it look a little younger?”