The ASA has particular areas of concern - here are extracts from their Website that explain how they are approached -
Taste & Decency - About 20% of all of the complaints received by the ASA are about advertisements that have caused offence. Judging these complaints is a delicate task, and the ASA interprets the British Code of Advertising, Sales Promotion and Direct Marketing, which states that advertisements should not cause serious or widespread offence, and that special care should be taken not to offend on the grounds of race, religion, sex, sexual orientation or disability. A lot will depend on the medium used and the context of any particular advertisement, and the ASA conducts regular research to gauge public opinion on these issues.
http://www.asa.org.uk/asa/focus/issue/Taste+and+Decency.htm
Social Responsibility -
•The use of shocking images that could cause undue fear and distress
•The depiction of scenes that could encourage people to behave in an irresponsible
or unsafe way
•The advertising of products, or their consumption, in ways that can be harmful to
health
•Advertising to children that could make them feel inferior, encourage them to pester
their parents, or result in their physical, mental or moral harm
http://64.233.183.104/search?q=cache:1lII8L7cRgIJ:www.asa.org.uk/NR/rdonlyres/5FBBCC12-53CD-4655-ACAF-4C911B8AD1A0/0/social_responsibility_20050928.pdf+advertising+standards+social+responsibility&hl=en&ct=clnk&cd=2&gl=uk
http://www.asa.org.uk/asa/focus/issue/Children.htm