The UK chairman of KPMG has admitted that the Big Four have become bloated and need reform as politicians renew calls for an overhaul of the embattled audit industry.

The collapse of Carillion has thrust the work of the construction giant's lead auditor KPMG — and its peers Deloitte, EY and PwC — into the spotlight, with MPs criticising the sector for "cursory audits" and "failed advice".