FTSE slides, energy stocks weigh

LONDON (Reuters) - Britain's top share index extended losses in the afternoon trading session, with energy stocks falling further after crude oil prices fell more than 1 percent on a firmer dollar and economic growth concerns. The blue-chip FTSE 100 index was down 1.6 percent by 1118 GMT, while the mid-cap index fell 1.2 percent. The UK oil and gas index declined nearly 3 percent, dragged down by a 2.2 percent fall in BP and a 2.6 percent drop in Royal Dutch Shell . Mid-cap oil company Tullow Oi