The U.K. practices of the world’s biggest accounting firms face a major overhaul as the Competition and Markets Authority (CMA) looks into whether they should be broken up.

The United Kingdom’s competition watchdog has outlined “serious” competition concerns caused by the Big Four’s dominance of the audit market and has proposed changes to legislation to improve the sector and allow other audit firms greater access.

Neil Hodge is a freelance business journalist and photographer based in Nottingham, United Kingdom. He writes on insurance and risk management, corporate governance, internal audit, compliance, and legal...