By Alistair Smout and Atul Prakash
LONDON (Reuters) - Britain's top share index hit a seven-week low on Friday and registered its biggest weekly loss in 10 months as drugmakers came under pressure from political scrutiny in the United States ahead of its Nov. 8 elections.
The blue-chip FTSE 100 (FTSE) index closed 1.4 percent weaker after falling to its lowest level since mid-September. The benchmark index fell more than 4 percent for the week, the biggest weekly drop since January.
Miners also slumped after a fall in some metals prices. The UK mining index (FTNMX1770) tumbled 2.3 percent, dragged down by a 1.8 to 4.6 percent drop in BHP Billiton (L:BLT), Anglo American (L:AAL), Randgold Resources (L:RRS) and Fresnillo (L:FRES).
The mid-cap FTSE 250 (FTMC) ended 1.8 percent lower. The domestically-focused index had rallied on Thursday following a court ruling that the British government had to consult parliament on triggering Brexit. However, traders said that growing uncertainties were hurting the market.
They said that next Tuesday's U.S. presidential election was weighing on sentiment. Republican Donald Trump has closed the gap on Democrat Hillary Clinton in the polls in recent days, and there is uncertainty in the market over what a Trump presidency would do to the economy.
Two U.S. lawmakers called on Thursday for an investigation into whether major pharmaceutical firms colluded to set prices for insulin and other diabetes drugs.
Drugmaker Hikma Pharma (L:HIK), down 6.8 percent, was the worst performer in the FTSE 100 index, with HSBC highlighting the risk that the company could be dragged into the inquiry.
"It's uncertainty around the election which is knocking sentiment at the moment, but pharmaceuticals will likely feel the heat whichever way it goes," said Jasper Lawler, market analyst at CMC Markets. "Clinton will probably be harsher on pricing on the sector, but Trump could be quite interventionist as well and take on these populist causes."
Friday's fall was broad-based, with only six FTSE 100 stocks staying in positive territory.
Paddy Power Betfair (L:PPB) was the stand-out gainer, rising 4.1 percent as it benefited from foreign exchange effects following a fall in sterling after the Brexit referendum, and better synergies from its recent merger.
The merger between Paddy Power and Betfair was completed in February this year.
"It seems like the drop in the pound came at just the right time, as the merger is starting to bear fruit, as they're using their higher market share to push both services," CMC's Lawler said.