Deloitte has been fined £6.5m over failures in its auditing of Serco, the outsourcing company, which itself is set for a multi-million-pound court penalty over its work for the UK government.

There has been a spate of fines for the Big Four accountancy firms – Deloitte, EY, KPMG and PwC – and questions over their culture and suitability for the job of auditing large corporations, in particular after the high-profile collapse of another government-contracted outsourcing company, Carillion, in January 2018. There have also been calls to break up the Big Four, which dominate the market.