Britain’s top medical association yesterday made a strong call for genetically modified foods to be labeled as such, allowing consumers to choose to avoid them until they are proven more safe for consumption. The British Medical Association, which represents 80 percent of Britain’s doctors, also called for gene-modified crops to be processed separately from conventional crops. The BMA report angered members of Congress and upped trade tensions between Britain and the U.S., which has refused to segregate gene-modified products. Four days ago, a bipartisan group of 36 senators sent a letter to Pres. Clinton asking him to stand up for American agricultural biotechnology at the World Trade Organization and upcoming G8 summit to avert a “looming trade conflict” with Europe.