The FTSE 100 rose 2.7% in morning trading, led by financials, housebuilders and travel companies, as the latest Brexit polls suggest the likelihood of Britain exiting the EU is diminishing.
The UK's blue-chip index was trading 2.6% higher at 6,176 points at 10.25am, led by domestic stocks as the latest Brexit opinion polls point to a shift in sentiment away from a Brexit vote.
The Royal Bank of Scotland was the top riser in the index, up 7.7% at 239.2p, followed closely by other financials, including Hargreaves Lansdown and St. James's Place.
Hargreaves is trading 7.2% higher at £13.18, while St. James's Place is up 6.3% at 875.8p. Lloyds and Barclays are also among the top risers in the index, up 5.9% and 5.4%, respectively.
Sterling volatility index hits six-year high as EU referendum nears
Meanwhile, housebuilders are also showing a strong performance, with Taylor Wimpey up 6.3% at 186.9p, and Barratt Developments trading 5.9% higher at 563p.
Travel companies also had a strong start to the day, with Thomas Cook up almost 7.2% and International Consolidated Airlines Group jumping 5% to 501.8p.
A vote to stay in Europe would be good for the pound, boosting Briton's spending power abroad, and therefore their propensity to travel.
Meanwhile, sterling is up 2.2% against the dollar, trading at $1.4665, and 1.5% higher against the euro at €1.2919.
The FTSE 250 is also making gains, up 2.5% at 16,838, though one of the stocks in the index, Circassia Pharmaceuticals, fell as much as 66% after a failed drugs trial.
Woodford Patient Capital trust, which holds a 4% in the pharmaceutical stock, joined the short list of losing stocks as a result, with a downward move of 0.6%.
FTSE 100 falls below 6,000 and sterling hit as Brexit fears dominate
Laith Khalaf, senior analyst at Hargreaves Lansdown, commented: "Waves from the Brexit vote are buffeting the UK stock market, tossing it up and down as the opinion polls shift this way and that.
"Until the vote is over we can expect more price swings, as markets struggle to price in a unique event that carries with it such a high degree of uncertainty.
"If you want to get an idea of what stocks will do well in the event of a vote to stay in the UK, it is worth taking a look at today's FTSE leader board.
"The market has clearly identified financials and house builders as beneficiaries of a vote to remain in the UK, with a sterling rally also indicating how the currency might move if we vote to remain in Europe."
