London equities ended lower on Wednesday, with traders on tenterhooks before the outcome of the US Federal Reserve's latest monetary policy gathering, analysts said.

London's FTSE 100 index of leading shares lost 0.40 percent to close at 6,348.82 points.

Investors have been speculating about when the Fed will start tapering off its $85 billion-a-month bond-buying programme, known as quantitative easing and which is credited with helping push global equities to recent highs.

Global equities and currencies have been sent into turmoil in recent weeks on expectations that Fed chairman Ben Bernanke will start turning off QE.

Investors are therefore anxious to see what Bernanke will say Wednesday at his traditional post-meeting press conference.

"Chairman Bernanke's question-and-answer session is being viewed as a make or break moment for equity market momentum, though whether we will actually garner any clarity on the Fed's timeframe for tapering their stimulus programme remains to be seen," said analyst Matt Basi at traders CMC Markets.

In London, supermarket giant Tesco was unscathed by investor anxieties, rising 2.59 percent -- 8.7 pence -- to 344.6 to become the top performer of the day.

Drinks maker Diageo followed, gaining 2.09 percent -- 39.5 pence -- to end at 1,925.5.

Temporary power supplier Aggreko was the biggest faller, losing 5.25 percent -- 92 pence -- to 1,660, followed by United Utilities Group which dropped 4.75 percent -- 34.5 pence -- to 692.

Vodafone was the most traded stock, with 132.14 million units changing hands, followed by Lloyds Banking Group with 111.84 million.

On the currency markets, the pound edged up to $1.5661 at around 5.20pm from $1.5630 the previous evening, while it rose to 1.682 euros from 1.1663 euros over the same period.