* FTSE down 0.7 percent ahead of U.S. non-farm payrolls

* Energy stocks retreat as crude falls below $70 barrel

* Miners stocks weakened by cheaper metal prices

* Broad retreat; drugmakers, life insurers lose ground

By David Brett

LONDON, July 2 (Reuters) - Britain's top share index was down 0.7 percent at midday on Thursday, as equities fell broadly, led lower by energy and mining stocks which fell on retreating commodity prices ahead of key U.S. payrolls data.

Energy companies, which gained in the previous session tracking higher oil prices, took most points off the index as crude dipped back below $70 per barrel CLc1.

BP (BP.L: Quote, Profile, Research), Royal Dutch Shell (RDSa.L: Quote, Profile, Research), BG Group (BG.L: Quote, Profile, Research) and Tullow Oil (TLW.L: Quote, Profile, Research) fell 0.9-1.7 percent.