By Helen Reid
LONDON (Reuters) - Britain's top stocks index fell on Wednesday as mining and materials shares sold off on a slide in metals prices after the Trump administration threatened further tariffs on China.
Earnings drove the lion's share of moves across the UK market, with retailer Next, power provider Aggreko, and contractor Capita among the most prominent.
Overall the FTSE 100 fell 0.8 percent by 0822 GMT, with miners the biggest weight as Rio Tinto results disappointed and copper prices fell.
A source said the Trump administration plans to propose slapping a 25-percent tariff on $200 billion of imported Chinese goods, having initially set levies at 10 percent.
Rio's shares <RIO.L> tumbled 3.6 percent after first-half results missed earnings expectations.
"The key places where the miss occurred was iron-ore and aluminium divisions - most exposed to recent cost inflation. This is likely to be the key point of discussion today," said Goldman Sachs analysts.
High-street retailer Next <NXT.L> fell to the bottom of the FTSE 100, down 5.6 percent after reporting a rise in full-price sales, though it maintained sales and profit guidance.
"Clearance rates were better than planned, adding 4 million pounds to profit, however this was largely offset by higher warehouse and distribution costs," said Goldman Sachs analysts.
Lloyds <LLOY.L> was a bright spot, rising 2.1 percent after the bank's first-half profit jumped 23 percent, in line with expectations.
"Though the bank set aside another £460 million for PPI mis-selling claims, the fact that saga is coming to an end, alongside a 23% jump in pre-tax profit to £3.1 billion, kept investors onside," wrote Connor Campbell, analyst at Spreadex.
This season has been characterised by sharp reactions to earnings. Goldman Sachs analysts said results-day moves across European stocks are the biggest since they began compiling data on this in 2003.
Overall UK stocks' earnings have been strong, with commodities driving the bulk of earnings growth. A weaker sterling has also helped the exporter-heavy index.
Among mid-caps, outsourcer Capita <CPI.L> fell 7 percent after reporting weaker than expected free cash flow and warning the return to sales growth would take time.
"Management's narrative regarding revenue momentum feels softer," said Jefferies analysts.
Aggreko <AGGK.L> topped the mid-caps with an 11.3 percent gain, hitting a seven-month high after the temporary power provider's first-half profit beat consensus forecasts.
And BBA Aviation <BBA.L> brought up the rear on the FTSE 250, hitting a near 18-month low after profits and margins missed forecasts.
"The Board's confidence for only 'modest' full-year 2018 growth, plus Signature's subdued first-half EBIT progress and the slowdown noted in its market backdrop may prompt trims around 3 percent to 4 percent to consensus FY18 EPS," said Jefferies analysts.
In small-caps, funeral provider Dignity <DTY.L> jumped 7.4 percent to the top of the index after it announced a three-year turnaround plan and reported a rise in half-year revenue.
(Reporting by Helen Reid; Editing by Raissa Kasolowsky)