GSK leads London's FTSE 100 lower GlaxoSmithKline was the worst performer on the FTSE 100 index this morning as the pharmaceutical company battles a Chinese bribery and corruption scandal. GSK shares were down 0.9 per cent at £16.99 following the news that Shanghai police had detained a British fraud investigator who had previously worked with the company. Chinese authorities have already arrested four of GSK's most senior Chinese executives in recent weeks as part of a probe into allegations of bribery. Overall, the FTSE 100 was down 0.2 per cent at 6,617.77, pulled down by weakness in the telecoms and oil and gas sectors. Mining stocks, however, were making gains and Randgold Resources was the index leader, up 3.1 per cent at £46.65. The gold miner benefited from a rally in the bullion price as well as a positive note from broker JPMorgan. Outsourcing companies remained under pressure following last week's announcement by the government that it was reviewing all contracts on pricing concerns. Serco Group fell 0.4 per cent to 621p, while Compass Group 1.2 per cent lower at 885.5p. G4S, however, rallied 1.2 per cent to 219.4p.