British taxpayers face a £24bn bill for tax relief awarded to oil and gas companies removing hundreds of North Sea wells, rigs and pipelines, the UK public spending watchdog has said. The National Audit Office (NAO) said the figure would climb if companies collapse and are unable to pay for cleaning up their operations, leaving the government to pick up the tab. The industry has contributed more than £300bn in tax revenues to the Treasury since the 1960s. North Sea…