Traders were unmoved by robust UK economic growth of 0.5% over the third quarter, three months after the Brexit vote, and instead focused on fears about the rising cost of living. Growth was down from 0.7% from the second quarter, but easily beat market forecasts of a 0.3% rise.
The Office for National Statistics said service sector activity rose by 0.8%, construction fell by 1.4%, agriculture fell by 0.7%, and manufacturing contracted by 1.0%.
But the FTSE 100 Index only edged up 1.8 points to 6960 in afternoon trading, after growth was driven almost entirely by the services sector with manufacturing and construction continuing to fall. The FTSE 250 Index fell 114 points to 17555.1.
Spreadex financial analyst Connor Campbell added: "2017 is set to see inflation rapidly expand, something that will put increasing pressure on Britain's growth."
Barclays was the highest riser in the top flight after reporting a 35% rise in pre-tax profit to £837m (£1.02bn) for the three months to the end of September as it profited from bond trading and selling off unwanted assets.
Chief executive James Staley said the bank had made "strong progress" in the quarter towards closing its non-core businesses and dealing with historical issues. Shares lifted 3.1p to 185p.
In afternoon trading the biggest risers in the FTSE 100 Index were Barclays (+3.1p to 185p), Relx (+16p to 1445p), Imperial Brands (+42.5p to 3923p), GKN (+3.4p to 315.4p) and AstraZeneca (+49.5p to 4826.5p).
The biggest fallers in the FTSE 100 Index were Barratt Developments (-44p to 432.00p), BT Group (-14.2p to 373.5p), Wolseley (-112p to 4241p), Provident Financial (-78p to 2963p) and Persimmon (-43p to 1649p).
In afternoon trading the biggest risers in the FTSE 250 Index were Fidessa Group (+156p to 2452p), Vesuvius (+21.8p to 370p), Kaz Minerals (+13.2p to 296p), Debenhams (+1.8p to 55.5p) and Big Yellow Group (+19p to 706p).
The biggest fallers in the FTSE 250 Index were Amec Foster Wheeler (-107p to 478.6p), Berendsen (-210p to 1021p), Galliford Try (-85p to 1220p), Hill & Smith (-35p to 1031p) and Hunting (-16.3p to 491.2p).