The three bodies are currently holding exploratory talks in an attempt to come up with a joint code for both agency and in-house lobbyists.
The talks coincide with moves to tighten the existing code, which only applies to agencies.
So far, the talks have been focused on agreeing a set of key principles of conduct that would underpin such a code. A recent draft is understood to have referred to four key principles of conduct: transparency and openness; accuracy and honesty; integrity; and propriety.
The final plans will be run by in-house lobbyists at major bodies such as the Charities Commission, the Confederation of British Industry and the Trades Union Congress.
One senior figure in the public affairs industry said it was ‘quite historic' that the three organisations looked set to join forces.
Robert Khan, chair of the CIPR's Government Affairs Group, stressed the talks were at an early stage but said a more wide-ranging code would be a positive development.
He said: ‘It's important that we strongly underline the probity of the industry - not just with empty platitudes but with a rigorous ethical dimension. A joint code that covers not just consultancies, but also in-house practitioners who make up the majority of the industry, is to be welcomed.'