Labour's push for Net Zero has been blamed for "destroying” British jobs by the head of one of the largest Labour-supporting trade unions.Gary Smith, general secretary of the GMB union, compared Sir Keir Starmer's premiership to Margaret Thatcher's, saying energy policies were “closing factories, hitting investment and hitting jobs".The Union boss has once again hit out at plans to phase out North Sea oil and gas in a direct attack on Ed Miliban…