I could not replicate the problem with Inkscape, neither with separate images (default) nor with embedded images. In other words: images in SVGs from Inkscape are displayed without distortion in Chrome, Opera, and Firefox.

Seems like Xara is generating SVG files that browsers don't like. Perhaps some transformations are to blame. I noticed, for example, that in Xara SVG files, the direction of the y-axis is changed, using a transformation of the group with ID "Document": scale(1 -1)