The FTSE 100 ended down 1.6%, with insurer Prudential and miner Anglo American among those trading ex-dividend. The midcap index fell 0.5%.
Minutes from the Fed's July 28-29 policy meeting warned of a highly uncertain path for recovery from the global health crisis that has hammered economic growth across the world.
(GRAPHIC: FTSE 100, S&P 500 and STOXX 600 - https://fingfx.thomsonreuters.com/gfx/mkt/azgvonmzqpd/FTSE%20YTD.PNG)
"(Fed) minutes are casting a shadow over markets and underline that any recovery is not going to be a straight line of advances," Markets.com analyst Neil Wilson said.
U.S. stocks have hit record highs despite the worries over the economic recovery, while in Europe and Britain stock indexes are yet to recover from falls caused by fallout from the virus. The FTSE 100 is lagging its peers in Europe and in the United States.
Real estate stocks <.FTNMX8670> <.FTUB8600> were one of the few sectors that gained on the day, benefiting from safe-haven demand.
On corporate news-driven moves, miner Antofagasta fell more than 5% after reporting a plunge in half-year earnings.
Along with Antofagasta's results, a drop in copper prices from a more than one-year high also hit miners, with Glencore, BHP and Rio Tinto falling between 2% and 4%.
Losses in the midcap index were limited by gains in Mike Ashley's Frasers Group along with a number of real estate stocks.
Frasers jumped 13% after it forecast growth of up to 30% in its new financial year, while electricals maker AO World added more than 3% as it said demand for its products and services continued even after its rivals reopened stores in July.
Infrastructure group John Laing plummeted 7%, marking its worst day since early-July after reporting a half-year loss and saying it was unlikely to meet its 1 billion pound investment target by the end of 2021.
By Muvija M and Ambar Warrick