Dear sumandwivedi,
I do agree with Dinesh V Divekar. However it should be into account, that the organization’s culture is the total: norms, believes, and attitude of any organization's workforce.
As an HR practitioner this is your responsibility to inform your senior management, that they are the focal point of the ethics in the working environment. Nevertheless in most of the management books; it is written that people are the main factor in shaping the organization behavior.
But practically most of the time, its senior management whom shaping the organization’s culture. For example if any employee is acting against the organizational rules and regulation. And policy is prohibited that action.
Although in this situation senior management are using from their authority and power to put off , for sure here the main factor of the organization culture’s shaping and building will be the senior management, thus there is some term like, physical contract , which employee is sign on date of joining with the organization and its has the legal aspect, and another one is the psychological contract Which is unwritten documents, either both of the parties are have some expectation from each other, like; honesty and integrity.
My strong recommendation to you, is to first of all talk with your senior management , and then you can draft any type of policies, i.e. Dress code policy, communication policy, code of conduct, etc.…