London's top-flight index crashed to a seven-week low as European markets endured a bout of US election jitters in the run-up to Tuesday's poll.
The FTSE 100 index sank deeper into the red, closing down 97.25 points to 6,693.26, as US national opinion polls showed the race to the White House was tightening between Donald Trump and Hillary Clinton.
Germany's Dax fell by 0.7% and the Cac 40 in France dropped by 0.8%, as market concern over the US presidential election spread across Europe.
The London market was extending its losses from the previous session, when it was left reeling from sterling's remarkable rally in the wake of a landmark ruling from the High Court, which stipulated that Brexit must face a parliamentary vote.
While Brexit uncertainty has been the bane of markets in recent months, the chance that MPs maybe able to water down the terms and keep Britain in the single market has helped the pound claw back some losses.
Sterling continued to push ahead on Friday, reaching its highest level since October 6 against the US dollar at 1.255.
The UK currency was given a leg-up by the greenback, which weakened after robust US employment figures came in shy of expectations.
Sterling was up 0.4% or 1.251 versus the US dollar and 0.3% higher against the euro at 1.125.
Neil Wilson, markets analyst at ETX Capital, said sterling now has 1.26 US dollars firmly in its sights as the US elections continues to weigh on the dollar.
"Importantly that's the level the pound traded just before the flash crash. At the very least, we can see the pound has just about recovered from that shock."
However, the price of oil took a tumble after tensions between Saudi Arabia and Iran re-emerged, threatening to unravel Opec's pact to curb supply. Brent crude slid 1.8% to 45.54 US dollars a barrel.
In UK stocks, betting giant Paddy Power Betfair was among a small number of blue-chip firms making gains on the London market.
Shares in the bookmaker were up more than 4%, or 355p to 8,935p, after it raised its full-year profit forecast following a third-quarter boost from the Brexit-hit pound.
The company saw revenue rise 25% to £404 million in the three months to September 30, as it benefited to the tune of £28 million from the translation of non-UK revenues due to the weakness of sterling.
On a constant currency basis, turnover grew 15%. Underlying earnings were up 53% to £113 million in the quarter and the group said it now expects underlying earnings for the full year to come in between £390 million and £405 million, against previous expectations of £365 million to £385 million.
The biggest risers on the FTSE 100 Index were Paddy Power Betfair up 355p to 8,935p, BAE Systems up 4.5p to 539p, Rolls-Royce Holdings up 5p to 712.5p, SSE up 8p to 1,571p.
The biggest fallers on the FTSE 100 Index were Hikma Pharmaceuticals down 119p to 1,626p, Dixons Carphone down 17.8p to 323.7p, Persimmon down 81p to 1,677p, Royal Bank of Scotland down 8.9p to 185p.