The blue-chip index followed Asian markets lower, despite a recovery in oil prices.
The FTSE 100 fell over 1% to 6,834.
UK supermarkets weakened on news that German discounter Aldi achieved record sales and announced a £300 million investment in its stores.
Tesco (TSCO), Sainsbury's (SBRY) and Morrisons (MRW) were pushed into the red.
Commodity stocks pulled the blue chip index lower with Polymetal (POLY) slipping 2.2% and Anglo American (AAL) declining 2.5%.
Housebuilders Taylor Wimpey (TW.) and Barratt (BDEV) slumped by 3.4%.
West Texas Intermediate (WTI) crude oil rose 1.3% to $45 and Brent crude oil rallied 1.7% to $46.69 per barrel, respectively.
Gold nudged lower to $1,336 per ounce and copper cheapened 0.6% to $4,806 per tonne.
Gross mortgage borrowing of £12.4 billion was 1% higher than August, according to the BBA.
BLUE CHIP RISERS AND FALLERS
WPP (WPP) nudged 1.7% lower after broker Jeffries International downgraded its rating from hold to buy and cut its price target.
Pharmaceutical firm Shire (SHP) retreated 1.8% following HSBC's downgrade from hold to buy and cut in price target.
MID CAP RISERS AND FALLERS
Scandal-hit Sports Direct (SPD) declined 5.3% despite an initial positive reaction to Mike Ashley taking over as CEO following Dave Forsey's resignation on Friday.
Broker Peel Hunt's downgrade from add to hold for events company UBM (UBM) accompanied a 2.4% slump in the share price.
SMALL CAP RISERS AND FALLERS
Malaysian data centre operator CSF (CSFG) plummeted 39.6% to 0.53p on news it intends to seek shareholder approval to delist from the AIM market.
Rig refurbishment specialist Lamprell (LAM) was one of the biggest risers on the London Stock Exchange, rising 10.5% to 70.75p after winning a $90 million contract from new client Master Marine. Lamprell will upgrade its mobile operating unit as an accommodation service vessel for Statoil's Johan Sverdrup field offshore Norway.
Investors were impressed by housebuilder MJ Gleeson's (GLE) 20.5% growth in annual pre-tax profit to £28.2 million and hiked dividend of 45% to 14.5p. The company said trading was 'business as usual' since the EU referendum.
Russian E&P business Zoltav Resources (ZOL) nudged 2% lower to 24p despite delivering a maiden pre-tax profit in the half-year to June, which reflected 'efforts on driving performance at Bortovoy's Western Gas Plant and on cost efficiencies'.
North River Resources (NRRP) fell 14.8% after reporting mixed results at its Namib project, which requires a critical period of assessment to determine how to proceed.
Green gas company Good Energy (GOOD) surged 11% to 266p following a positive article in The Mail On Sunday.
Brand experience specialist SpaceandPeople (SAL) crashed 30.4% to 27.5p after swinging from a profit of £62,000 to a £174,000 loss in the first half of the year due to 'subdued trading'. The firm also suspended dividends temporarily.
Respiratory disease-focused drug developer Verona Pharma (VRP) got a shot in the arm following upbeat management expectations for smokers cough treatment RPL554. It also revealed Piers Morgan as chief financial officer, who used to be chief executive of C4X Discovery (C4XD).