From 1 May, pharmaceutical companies must ensure such links are declared when a health professional writes or speaks in public about a subject related to the company.
New rules from the Association of the British Pharmaceutical Industry will also require companies to make consultant fees publicly available from 2012, although this information can be anonymised.
Companies must also refer to absolute risks in scientific claims whenever figures relating to a relative risk are stated.
The guideline states: 'Referring only to relative risk, especially with regard to risk reduction, can make a medicine appear more effective than it actually is.
'In order to assess the clinical impact of an outcome, the reader also needs to know the absolute risk involved.'
The rules also introduce restrictions on promotional aids that can be given to health professionals.