The BBC's Royal Charter does not specify the operating rules (bias, propaganda, etc.). These are dealt with by Protocol B2 which explains how the BBC Trust works to ensure that BBC output meets appropriate editorial standards...
"The role and duties of the Executive Board...
B2.2 The Executive Board is responsible for ensuring compliance with the Editorial Guidelines, the Ofcom Broadcasting Code as it applies to the BBC and any other relevant codes, policies and guidelines and is accountable to the Trust for such compliance in all BBC output. In particular, the Executive Board must do all it can to ensure that controversial subjects are treated with due accuracy and impartiality in all output that consists of news, or deals with matters of public policy, or of political or industrial controversy."
...which brings us back to the Editorial Guidelines mentioned in my post above.
It is not possible to prove non-compliance unless you see or hear the alleged evidential breach of the 'rules' within broadcast content. That content is governed by editorial standards, therefore you are making a complaint based on editorial content. The procedures set out in the Protocol specify:
Stage 1 - an editorial complaint is made to the BBC Executive. If you are not satisfied with the response, contact the department which replied explaining why and requesting a further response to the complaint.
Stage 2 - still not satisfied, complaint will normally be referred to the Editorial Complaints Unit.
Stage 3 - still not satisfied, you may ask the BBC Trust to consider an appeal against the finding.
http://www.bbc.co.uk/...agreement/index.shtml