The FTSE 100 index was down 16.24 points, or 0.3 per cent, at 5,929.61, having closed 0.4 per cent higher at a nine-month closing peak on Wednesday following six days of consecutive gains.
The index recovered slightly in afternoon trading from early falls following encouraging unemployment and retail data from the United States.
However, shares fell back towards the intraday trough of 5,918 after US House Speaker John Boehner accused President Barack Obama of being willing to “slow walk” the economy towards fiscal crisis.
Federal Reserve Chairman Ben Bernanke had set the tone for the day's trading, warning that monetary policy won’t be enough to offset damage if politicians fail to avert the “fiscal cliff” of steep tax hikes and budget cuts which could throw the world’s biggest economy into recession.
AstraZeneca was the most heavily traded stock in the index, trading over twice its 90-day daily average volume, while FTSE volume was at 70 per cent.
The drug company lost 2.8 per cent and took the most points off the index as it said an experimental rheumatoid arthritis drug proved inferior to Abbott Laboratories’ Humira in a clinical study. Profit taking was seen as a theme across the index, with the FTSE expected to resume its upward path heading into the year end despite the session’s losses.