Jim, the Mirror is a Labour paper.
Wiki, "On 4 May 2010, the newspaper printed a picture of Conservative Leader David Cameron with a giant red cross through his face. The headline read "How to stop him" in reference to the general election two days later, thus confirming the Daily Mirror's Labour allegiance. "
" The Daily Mirror was the only leading national newspaper to remain loyal to Labour and Gordon Brown at a time when opinion polls showed them on course for their worst election result since 1983"

Musket,
So, where do opinions come into it?

I am interested in opinions about how to stop them doing it again.

What is a "left wing" newspaper? Why give it credence versus any other rag?

You people dismiss anything appearing in Right of centre papers like Telegraph and Mail.