You can read the whole (one side of A4) statement via the link above, but the interesting bit is this:
A number of considerations have been taken into account in reaching this
conclusion, including the fact that the Consumer Rights Act 2015, which gives the
CMA new powers enabling it to secure compensation for consumers, only came into
effect on 1 October 2015, which is after the affected vehicles were sold, and that VW
has committed to fixing the affected vehicles. This means that in this case, the
CMA’s civil enforcement powers have limited application to the alleged wrongdoing
that took place.
Regarding a criminal investigation, an important consideration was that the alleged
misconduct at the root of this issue appears to have taken place outside the UK,
notably in Germany, and is the subject of a criminal investigation by the German
authorities. In view of this, the CMA has had regard to the general presumption that
a prosecution should take place in the jurisdiction where the majority of the more
serious criminality occurred.
'via Blog this'