The UK government’s decision to keep the windfall tax on North Sea oil and gas operators could wipe out as much as $20 billion (£15 billion) of potential investment in Britain’s offshore oil and gas output, according to a Wood Mackenzie estimate cited by the Financial Times. The government last week kept the windfall tax on operators in the Budget, dealing a blow to the industry. Keeping the Energy Profits Levy (EPL), as the windfall tax is officially known since it was first introduced by a Conservative government at…