Many NHS trusts in England are failing to log, track or disclose information on conflicts of interest among staff, it has been claimed.
While healthcare professionals are obliged to divulge any potential conflict, the current system for recording them is "not functioning adequately", according to a report published in journal BMJ Open.
Public trust in the profession could be undermined by a lack of transparency, the researchers warned, as they called for the establishment of a central statutory body to ensure NHS trusts tighten their policies.
NHS England has issued standards to trusts which state that all staff should declare potential conflicts of interest to their employers, and that these should be recorded in a gifts and hospitality register.
Copies of these registers for the financial year 2015 to 2016 were requested from 236 NHS trusts in England as part of the study.
Of the 185 registers received, the researchers found only 31 (16.7%) contained fields recording the name of the recipient, donor and the cash amount received and incomplete fields were "common".
They said a US-style system should be established, which requires all payments to doctors to be declared on an openly accessible central database.
"Information on conflict of interest is poorly collected, poorly managed, and poorly disclosed by NHS Trusts in England," the researchers said.
"The ongoing absence of transparency around conflict of interest in the UK may undermine public trust in the healthcare professions.
"Simple clear legislation and a requirement for open disclosure of conflict of interest to a central body, similar to that in the US, would present a simple and effective solution."
Direct gifts and incentives have been banned by trade body the Association of the British Pharmaceutical Industry since 2010.
But pharmaceutical companies can pay clinicians to deliver professional development lectures, sponsor their attendance at conferences or educational events, and provide training to other clinicians.
The pharmaceutical industry reported around £115 million was spent in this area in 2015.
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