As government outrage deepens over leaks of secret tax policy consultations by PwC personnel, industry figures were describing the scandal as a watershed event for the government which is wrestling with whether it can trust advice from big four firms on whom it relies to help shape new tax laws.

The Tax Practitioners Board went almost entirely unnoticed last November when it deregistered PwC’s former head of international tax, Peter Collins, and sanctioned the firm for its failure to monitor conflicts of interest by partners who shared confidential information with clients.