This isn't party politics.
The CPS exists to ensure that wrongdoers are brought to justice, victims of crime are supported and that people feel safer in their communities.
It
Advises the police on cases for possible prosecution
Reviews cases submitted by the police for prosecution
Where the decision is to prosecute, determines the charge in the more serious and complex cases
Prepares cases for court
Presents those cases at court
http://www.cps.gov.uk/yourcps.html

