LONDON'S FTSE 100 Index has slipped for a second day running, dragged down by insurance giant Admiral which plunged after posting weaker-than-expected half-year results.

The benchmark UK index fell 34.77 points to finish at 6859.15, ahead of its session low of 6849.9.

Car insurer Admiral proved to be the biggest loser on the FTSE, ending down more than seven per cent for the day despite announcing a 23 per cent dividend increase.

Investors seemed spooked by weaker-than-expected half-year profits triggered by volatility around the Brexit vote.

Shares were off 173p to 2081p.

On the currency markets, sterling momentarily rose following positive jobless figures, before paring back to trade 0.3 per cent lower against the dollar at 1.30 US dollars.

The pound was also down 0.2 per cent against the euro at 1.15 euros.

It came after the Office for National Statistics reported that unemployment hit its lowest level since the summer of 2005 at 4.9 per cent

The employment rate reached a record high of 74.5 per cent, with 31.8 million people in work in the three months to June - 172,000 more than the previous quarter.

The claimant count, including those on Jobseeker's Allowance, fell by 8,600 to 763,000 in the period after the Brexit vote between June and July.

Job vacancies were down 7,000 between May and July to 741,000, a period briefly covering Britain's vote to leave the European Union.

Negative sentiment also hit stocks in mainland Europe, with the French CAC 40 finishing down 0.96 per cent while the German DAX ended 1.3 per cent lower.

In oil markets, Brent crude prices were up 0.5 per cent to 49.45 US dollars a barrel thanks to a surprising drop in US crude inventories at 2.5 million barrels against analyst expectations for a 522,000 barrel reduction.

In UK stocks, shares in infrastructure giant Balfour Beatty raced ahead after it narrowed its losses as a turnaround plan under boss Leo Quinn began to bear fruit.

Shares were up more than three per cent or 7.4p to 251.8p, as pre-tax losses for the first half of the year came in at £21 million, down from £150m in the same period in 2015.

Revenues were broadly flat at £4.1 billion and the firm reinstated its dividend at 0.9p per share.

Struggling aerospace and defence firm Cobham stepped up 0.6p to 160.9p after it parted company with chief executive Bob Murphy and replaced him with David Lockwood, currently boss of tech company Laird.

Earlier this month Cobham reported losses of £38m, which was preceded by a profit warning and an emergency £506.7m rights issue to reduce its debt pile.

The biggest risers on the FTSE 100 were Barratt Developments up 6.5p to 448.2p, CRH up 23p to 2,535p, Whitbread up 34p to 4,035p, and BT Group up 3.2p at 395.8p.

The biggest fallers were Admiral Group down 173p to 2,081p, London Stock Exchange Group down 84p to 2797p, Antofagasta down 16p to 542.5p, and Fresnillo down 55p to 1,927p.