LONDON'S top flight index dropped back below the 7,500 mark as the market suffered a bout of jitters ahead of Thursday's General Election vote.

The FTSE 100 Index was down 46.33 to 7,478.62, as the leaders of Britain's biggest parties made last-ditch bids to secure votes as they entered the final furlong in the race to Downing Street.

However, sterling was enjoying a brighter session on the currency markets, lifting 0.4 per cent against the US dollar at 1.295 and climbing 0.6 per cent versus the euro at 1.151.

Elsewhere in Europe, Germany's Dax was marginally down at 0.1 per cent, while the Cac 40 in France also dropped 0.1 per cent.

London's blue-chip energy stocks suffered as the price of oil fell on concerns over Opec's production cuts amid escalating tensions in the Middle East.

Brent crude was down 3.5 per cent - or one dollar and 73 cents - to $48.39 a barrel, with traders focussing on the decision by Saudi Arabia and a number of other Arab countries to sever ties with Qatar over claims that the country has been supporting regional terror groups.

Royal Dutch Shell B and BP were down 21.5p to 2,115p and 8.1p to 456.8p respectively.

In UK stocks, Royal Bank of Scotland (RBS) surged after the lender avoided a lengthy courtroom battle with shareholder groups over a 2008 rights issue overseen by disgraced former boss Fred Goodwin.

The RBoS Shareholder Action Group, which brought the £700 million lawsuit and represents 9,000 retail investors and 18 institutions, accepted an 82p-per-share deal.

Shares in RBS rose more than one per cent, or 3.4p to 255.1p.

Advertising giant WPP was down more than two per cent after making a trading update at its annual general meeting (AGM).

The firm said reported revenues rose 16 per cent to £4.8 billion in the first four months of the year, thanks to a boost from the Brexit-hit pound.

WPP was also dealt a bloody nose during the AGM, with a large tranche of shareholders voting against a £48m pay package for chief executive Sir Martin Sorrell.

More than 21 per cent of investors opposed or abstained when asked to vote on the remuneration report.

While the vote was not binding, the level of discontent will be embarrassing for the FTSE 100 firm, which cut Sir Martin's total pay to £48.1 million for last year, from £70.4 million for 2015.

However, the level of protest over WPP's new remuneration policy, which will hand executives lower long term incentive awards, was at a more modest 10 per cent.

Shares in the firm were down 45p to 1,676p.

On the second tier, housebuilder St Modwen Properties pushed higher after a healthy trading update.

Shares rose six per cent, or 20.8p to 353p, after reporting that its half-year performance was in line with expectations following "robust demand" for new homes.

The biggest risers on the FTSE 100 Index were Persimmon up 48p to 2,393p, Lloyds Banking Group up 1.14p to 70.1p, Standard Life up 5.9p to 381p and Taylor Wimpey up 2.8p to 181.8p.

The biggest fallers on the FTSE 100 Index were Shire down 145.5p to 4,376.5p, WPP down 45p to 1,676p, Babcock International down 18.5p to 906p and Johnson Matthey down 60p to 2,979p.