LONDON'S blue-chip index struggled to gain ground after a delayed opening on Thursday due to a technical error.

The FTSE 100 fell 7.97 points or 0.10% to 7,704.4 during the session, having opened an hour later than usual.

The fall came despite a surge in oil prices, which lifted the likes of BP and Shell.

Oil prices pushed higher when it emerged that Venezuela was nearly a month behind on crude deliveries, outweighing fears of production increases from the Organisation of Petroleum Exporting Countries (OPEC).

Brent crude rose 1.52% towards the end of the session to $76.942 a barrel on the news, while BP and Shell were some of the top risers on the FTSE 100.

Fiona Cincotta, senior market analyst at City Index, said: "With two weeks remaining until the OPEC meeting in Vienna, we are expecting an increase in volatility as investors weigh up the probability of an increase in production against the increasing supply problems in Venezuela and Iran."

In currency markets, concerns about a hard Brexit weighed on the pound. Against the euro, sterling was down 0.28% to 1.135. The currency edged up 0.1% to 1.343 against the US dollar.

SSE's shares climbed during the day, despite the energy giant receiving a slap on the wrist from the regulator.

The firm was ordered to pay £1 million for sending out inaccurate and misleading annual statements to 580,000 pre-payment meter customers. Regulator Ofgem said an investigation found SSE sent out 1.15 million such statements. Shares were up 9.5p at the close to 1,356.5p.

Shares in outsourcer Mitie fell 0.5p to 195.2p after it insisted it was on track amid a swingeing overhaul, despite reporting a drop in annual earnings after a tough past year.

The group reported a 6% fall in underlying earnings to £77.1 million for the year to March 31, although revenues rose 2.8% to £2.2 billion.

Spread-betting firm CMC Markets has cheered record annual profits sending its shares up 8.2p to 195.2p.

The group reported a 24% rise in pre-tax profits to a record £60.1m for the year to March 31.

Marks & Spencer boss Steve Rowe saw his pay slashed last year after profits at the high street giant plunged, but will still walk away with £1.1m.

Mr Rowe, who is overseeing a drastic store closure plan, stomached a 31% reduction in total pay from £1.64m in 2017. Shares fell 1.13% or 3.3p to 289.2p.

Meanwhile, Debenhams' stock was hit by the news that rival House of Fraser was to close more than half its stores. The department store's shares fell by 4.15% or 0.88p to 20.32p as traders took a poor view of its prospects.

But Joules defied the retail gloom, with its shares rising 4.26% or 14p to 343p when it said it profits would beat expectations for the year.

The retailer said on Thursday that its profits for the year ended May 27 2018 would be "marginally ahead" of the forecast £12.6m.

The biggest risers on the FTSE 100 were BP up 12.7p to 589.6p, United Utilities up 15.2p to 786.4p, Royal Dutch Shell up 39p to 2,621p and NMC Health up 50p to 3,490p.

The biggest fallers on the FTSE 100 were Mediclinic International down 33.6p to 555.4p, Vodafone Group down 9.1p to 187.5p, Sainsbury's down 9.5p to 303.6p and Burberry Group down 61p to 2,116p.