A UK drivers licence also can be used in place of a passport for ID purposes and certain travel (not to the same extent as an EU ID), that doesn't mean it is a passport either.
I looked at this point a few months ago. My understanding on this is that the UK des not issue ID cards, and the UK driving licence card is not an ID card. I think the only instance you can use it as a travel document is for UK dometic flights where needed by the airline (and possibly Ireland due to the common travel area?).
For member states of the EU valid travel documents are a EU passport or government issued ID card. For countries who do not issue ID cards (Denmark, UK, and Ireland) an EU passport is the only option.