Brent crude oil remained mired below $45 a barrel on Thursday leaving it further in a bear market as traders continue to lose faith in Opec’s ability to balance supplies. Oil prices have now dropped by more than 20 per cent since the start of this year, with Brent on course to post its worst first half since 1997 and energy stocks getting hit. Brent fell under $45 on Wednesday for the first time in 2017. The sell-off has accelerated since late May when Opec extended a deal with Russia and other producers to cut supplies by 1.8m barrels a day. US shale producers have increased the rate of drilling, stepping into the void and showing they can compete in a world of sub-$50 oil. Many traders believe the price slide will only be arrested when US shale drillers are either forced to slow their expansion plans or Opec kingpin Saudi Arabia agrees to lead the cartel in bigger supply cuts. Brent, the international benchmark, was down a further 0.2 per cent on Thursday at $44.73 a barrel, after finishing the previous session down 2.6 per cent at $44.82. US benchmark West Texas Intermediate fell 0.2 per cent to $42.44, extending Wednesday’s 2.3 per cent drop.