Controversy over conflict of interest at the US Food and Drug Administration deepened yesterday amid allegations in the British Medical Journal that senior staff attempted to discredit a safety official who told senators that the agency researchers, who worked with companies on drug approvals, had authority over the agency's drug safety office.

Last week, David Graham, an official at the FDA for 20 years, told a Senate hearing into the withdrawal of Merck's painkiller Vioxx, that the US public was "virtually defenceless" against dangerous medicines.