Drugs companies will need to declare all links to health charities under new pharmaceutical industry guidelines coming into force on 1 May.
A spokesman for the Association of the British Pharmaceutical Industry said one of the reasons behind its revised code of practice was the increasingly high profile of patient groups and health charities.
"We felt that in the past ten years they have come forward as lobbying groups and often enter into partnerships with pharmaceutical companies," he said.
Under the new guidelines, companies must publish, either on their websites or in their annual reports, a list of all the patient organisations they give money to, whether as sponsorship or donations.
There must also be a written agreement with every organisation, spelling out the exact terms of the relationship and the funding of every significant activity.
Although the code is self-regulatory, the spokesman said the ABPI had a process of 'naming and shaming' those that breached it.
The guidelines were introduced on 1 January, but the grace period expires at the end of April. Their implementation should help charities avoid situations such as that encountered by Diabetes UK - its sponsor Eli Lilly was censured by the medicines watchdog after omitting to put its own logo next to the charity's logo on a company-produced leaflet (Third Sector, 1 March).
Cancer Research UK and the Alzheimer's Society, both of which accept pharmaceutical donations but also have ethical guidelines, welcomed the review.
Maxine Taylor, director of policy and communications at CRUK, said: "This is the biggest review of its kind for more than ten years. It should lead to a more transparent and open relationship between the voluntary and pharmaceutical sectors."
A spokeswoman for the Alzheimer's Society said: "We fully support the new ABPI requirements. There shouldn't be a black and white attitude to pharmaceutical funding, and an open policy will lead to greater public understanding.
"However, the requirements won't affect the Alzheimer's Society because we have always had a clear and transparent ethical policy on our work with pharmaceutical companies."
Dr Marcus Roberts, head of policy at Mind, which does not work with the industry, also welcomed the move. "Large industries, such as the pharmaceutical industry, have the resources to distort research or policy agendas," he said. "Mind's policy is not to accept money from or hold shares in pharmaceutical companies, because it could compromise our position on patient choice in the use of medication."