The CPS state that the same criteria regarding whether or not a person is charged with an offence are used in all but the most minor of cases - essentially it is a judgement call as to whether or not a conviction is likely on the evidence available.

The criteria they have to follow in making a decision is laid out in the "Code for Crown Prosecutors"

http://www.cps.gov.uk/publications/code_for_crown_prosecutors/index.html

I don't understand the case you are trying to make - there seems to be little evidence to support your accusation 🙂