Britain's top shares fell by midsession on Friday, with declines in commodity assets outpacing gains in defensive stocks as investors fretted ahead of U.S. economic growth data from the United States, according to Reuters. By 1044 GMT, the FTSE 100 was 29.05 points, or 0.6 percent, lower at 5,284.90, having lost a modest 0.1 percent on Thursday. The energy sector was the biggest underperformer on the blue-chip index. Crude oil prices slipped as demand worries mounted. BP fell 1.4 percent. The oil major remained hamstrung by events related to the Gulf of Mexico oil spill. A panel of U.S. judges heard arguments from lawyers on Thursday on how piles of spill-related lawsuits against BP should be merged. Miners were also edging lower as appetite for risk faded, with BHP Billiton and Xstrata among the worst performers, down 1.5 and 1.3 percent, respectively. India-focused mining group Vedanta Resources Plc fell 1 percent as it posted first-quarter results and reported output fell from a record 7.8 million tonnes in the fourth quarter. Anglo American dipped 0.5 percent after it reinstated dividends but warned about delays and higher costs at its key iron ore project in Brazil. First-half profit doubled on higher prices. "We are seeing light volumes with traders shipping off on their summer holidays, so movement either way has been accentuated but there is no doubt there is an air of caution ahead of the U.S. data," said Jimmy Yates, head of equities at CMC Markets. Wall St stock index futures pointed to a lower start on Friday as investors stayed cautious ahead of U.S. GDP data due at 1230 GMT. Friday's GDP number is widely expected to show U.S. economic growth slowed in the second quarter, with markets fretting about the possibility of a double-dip recession. St. Louis Federal Reserve Bank President James Bullard said on Thursday he is worried about the risks the United States might fall into a Japan-style quagmire of falling prices and investment. "There a concern that the recovery is faltering in the U.S. and although the double dip might be averted it looks like being a slow and arduous recovery," said Giles Watts, head of equities at City Index. South African investment bank and asset manager Investec dropped 2.3 percent after reporting first-quarter results. CONSUMER WOES Adding to the jitters, British consumer morale fell to its lowest in almost a year in July as worries about the impact of government spending cuts drove expectations for the next 12 months to their lowest since the deepest point of the recession. Travel firms Tui Travel and Thomas Cook fell 2.6 and 1.8 percent respectively. On the upside, British Airways rose 2.6 percent. The embattled airline's quarterly pretax loss widened 10.8 percent to 164 million pounds ($256.4 million) after trade was hit by a volcanic ash cloud and strike-related disruption. However, the loss was almost 100 million pounds narrower than BofA Merrill Lynch had forecast, as the broker repeated its "buy" rating. Reflecting the caution among investors, defensively perceived stocks were among the biggest risers on London's blue-chip index. United Utilities, Severn Trent and National Grid rose 1.8 to 4.2 percent.