The FTSE 100 <.FTSE> index was seen falling on Tuesday in tandem with overnight drops on Wall Street and in Asia, as fears over the euro zone debt crisis resurfaced following a referendum move by Greece.
Greece's prime minister, George Papandreou, has threatened the euro zone's debt solution plans with a shock announcement he will hold a referendum on the latest bailout deal for his country.
Concerns are that irrespective of what was agreed in Brussels, the Greek people may choose to reject the austerity measures and opt for a full blown default instead, said Jonathan Sudaria, night dealer at Capital Spreads.
Financial bookmakers expected Britain's blue-chip index to open down as much as 61 points, or 1.1 percent, on Tuesday.
The index closed down 158.02 points, or 2.8 percent, on Monday at 5,544.22, its biggest percentage fall since September 22. However, it still posted a gain of 8.1 percent for October, its biggest monthly gain since July 2009 and snapping a five-month losing streak.
U.S. blue chips <.DJI> dropped 2.3 percent on Monday, closing its best month in 20 years on a down note as the failure of futures trading firm MF Global Holdings and new worries about Europe's debt crisis hammered financial shares.
Asian shares and commodities fell on Tuesday after the announcement by Greece, ahead of a key G20 meeting later this week.
On the economic front, investors will eye the final reading for British third-quarter GDP, due at 9:30 a.m., with growth forecast at 0.4 percent both quarter-on-quarter and on an annualised basis.
Ahead of that number, the Nationwide house prices survey for October will be released at 0700 GMT, with the October Markit/CIPS manufacturing PMI report due at 9:28 a.m.
Across the Atlantic, investors will be focussed on the start of the latest two-day U.S. Federal Reserve meeting, with the FOMC due to make an announcement on monetary policy after the London close on Wednesday, although no changes were expected.
Among a batch of U.S. data due on Tuesday, October's ISM report and September construction spending numbers will both be released at 3 p.m.