Canada’s Green Party, which prides itself on its environmentalism, has admitted to photoshopping an image of its leader, Elizabeth May, to show her holding a reusable plastic cup — attracting accusations of hypocrisy from its political opponents.

In the original photograph, Ms. May, an activist and lawyer who has led the party since 2006, is shown holding what she said was a compostable disposable cup while at the Sidney Street Market in British Columbia last year.

But in the edited photo she is shown holding a plastic reusable cup with the Green Party logo and a metal straw.

Ms. May said she was “completely shocked” when she heard about the photoshopping and had known nothing about it. Green Party officials said the editing wasn’t done to conceal anything because the original cup was also environmentally friendly. Ms. May explained that a well-intentioned party staff member did it to brand the image with the party’s logo.