Big banks are being slammed for being “subsidised by the taxpayer” and failing to pass on higher interest rates to savings and current accounts for customers. This comes amid the wave of bank branch closures which has seen 6,000 locations from lenders such as Santander, Barclays and Halifax close since 2015. Mark Mullen, the chief executive of Atom Bank, is hitting out at the country’s biggest financial institutions and calling for change in the banking sector. He is among the 120 business leaders who have signed an open letter backing the Labour Party’s plan for the economy ahead of the upcom…