London's FTSE 100 Index remained in negative territory and the pound gave back gains against the US dollar amid last-minute General Election nerves.
The top tier fell 28.64 points to 7449.98 as jitters over the result continued to weigh on stocks, with traders unconvinced over the polls.
Sterling fell 0.1% to 1.29 US dollars, having earlier hit a two-week high, although it edged 0.2% higher to 1.15 euros as the single currency weakened after the latest European Central Bank forecasts.
The final opinion poll of the campaign suggested the Conservatives were on course to win the election with a clear lead over Labour.
But overall the polls painted a mixed picture as the campaign drew to its conclusion.
David Madden, market analyst at CMC Markets, said: "Some investors have less confidence in the polls, in the wake of Brexit and President Trump.
"The UK stock market would prefer a Tory victory as the party is more in favour of free market economics than Labour. The ground lost by the Conservatives in the past couple of weeks has rattled some traders."
The pound also lost its earlier gains against the dollar amid poll uncertainty.
Experts said the bigger the margin of any Conservative win, the greater the negotiating power for Mrs May on Brexit terms.
On Wall Street, the Dow Jones Industrial Average edged 0.1% higher, although investors were focusing on Washington, where former FBI director James Comey was testifying as part of a congressional investigation into Russia's possible election meddling.
Among stocks in London, mobile phone giant Vodafone led the day's declines, down 5% or 11p to 218p.
Advertising giant WPP followed it on the list of share losers, down another 3% or 45p to 1631p after a 2% drop the previous session following an update that revealed a slight slowdown in growth in April.
The firm was also dealt a bloody nose during its AGM, with more than 21% of shareholders refusing to back a £48 million pay package for chief executive Sir Martin Sorrell.
Elsewhere, regional airline Flybe rose 0.5p to 33.5p, despite swinging into the red with a £19.9 million pre-tax loss for the year to March 31, compared to a profit of £2.7 million the previous year.
But FTSE 250-listed classified cars website AutoTrader dropped 3% or 13.2p to 418.5p in spite of annual figures showing profits accelerated last year.
The firm said full-year operating profit revved up by 18% to £203.1 million while on a pre-tax basis profit rose 23% to £193.4 million.
The biggest FTSE 100 risers were Ashtead Group up 48p to 1640p, Glencore ahead 5.9p to 288.9p, Rio Tinto 57.5p higher at 3224p and Next 66p stronger at 4352p.
The biggest FTSE 100 fallers were Vodafone down 11p at 218p, WPP off 45p to 1631p, Imperial Brands 79.5p lower at 3547p and Diageo 45p weaker at 2285p.
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