‘They’ being whoever doctored the image, and not the Labour MP.
It does (once again) raise a valid point about verification of images. Some kind of checksum or (god help us) blockchain based confirmation that an image hasn’t been altered.
Obviously any resizing of an image would screw this up, but there are already lots of apps that can find duplicates despite different resolutions.
I agree if the MP themselves (or one of their staff) had tweaked the image this would be more serious. Did anyone work out the original source of the modified version?