The Competition and Markets Authority (CMA) has ordered that Britain's top 350 listed companies must hire two auditors to loosen the grip of EY, KPMG, Deloitte and PwC that individually check the books of all but nine of those companies.

It forms a package of measures from the CMA aimed at improving audit quality and restoring trust after accounting failures at construction company Carillion and retailer BHS.

Though the changes are likely to take some time to make it into law, joint audits in France have enabled smaller rivals like Mazars to work alongside the Big Four and win the confidence of bigger clients.

They also feature in Sweden and Spain, but were ditched in Denmark due to the higher cost, with estimates ranging from about 20 percent to far higher.

"We know it works and we know it will work in Britain and will create a markedly different market that is much needed," said David Herbinet, the London-based global head of audit at Mazars.

According to the International Accounting Bulletin (IAB), Deloitte earned $43.2 billion globally in audit and consultancy fees in 2018 - a fifth of the market - while PwC earned $41.9 billion, EY $35 billion, and KPMG $29 billion.

Smaller competitors BDO and Grant Thornton earned $9 billion and $5.4 billion, respectively.

Checking the books of big, international companies with subsidiaries across the world has long been the preserve of the Big Four given the need for a cross-border network of partners and big spending on IT.

Deloitte, for example, employed 286,000 staff in 2018 compared with 80,000 at BDO and 52,686 at Grant Thornton, according to IAB.

PwC has spent a billion dollars on cloud computing alone in recent years, dwarfing the IT spend of BDO or Grant Thornton.

BDO and Grant Thornton audited just nine of the 350 top listed companies in Britain, the rest checked by the Big Four, Britain's accounting regulator, the Financial Reporting Council, has said.

FRENCH WAY

KPMG questioned the capability and willingness of smaller auditors to break into the top end of the market.

Big Four officials say privately that smaller rivals benefit from the current situation by having more opportunities to cream off the more lucrative consultancy work, especially now the Big Four won't sell advisory services to audit clients.

Smaller auditors have dismissed this view.

KPMG said that for BDO, Grant Thornton and others to audit big clients they will have to very quickly deliver multiple, large-scale, complex global audit work in a short time.

"Shareholders, audit committees and the regulator must have total confidence in the ability of these firms to complete this work before the market can move ahead with this recommendation," KPMG said.

Deloitte's UK managing partner for audit, Stephen Griggs, said joint audits were unproven in Britain and some countries had moved away from them due to big cost increases and little company and investor interest.

"In the only market where joint audits are used extensively, France, the vast majority of audit mandates in the CAC 40 are held by Big Four firms," Griggs said.

Joint audits have been in place in France for about 50 years, but only changed the market after regulators ruled in 2011 that they must be "balanced", meaning a Big Four firm cannot have the lion's share and leave crumbs for a challenger.

The CMA said only 44 percent of the 120 top listed companies in France are audited by two Big Four firms, and challengers often have around 40 percent of the joint audit.

Companies and investors have already cast doubt on the ability of joint audits to improve audit quality and avoid another Carillion or BHS.

"We remain unconvinced of the value of joint audits, as there is little evidence that they actually lead to the better quality audits that investors want to see," said Chris Cummings, chief executive of The Investment Association, which represents asset managers in Britain.

The CMA has said the biggest, most complex companies listed in the UK - estimated to number around 30 - would be exempt from the joint audit requirement.

Gervase MacGregor, head of risk and reputation at BDO, said market caps on the Big Four would diversify the market faster, a step the CMA considered but has not recommended.

"We will be gearing up and making this commitment," MacGregor said, referring to preparing for joint audits.

He said that over time Big Four audit market share in Britain would stagnate, with BDO already getting job enquiries from Big Four partners who see better promotion prospects at one of the smaller firms in a reverse of the historical situation.

Mandatory joint audits will need legislation and it could take several years before a new law is in place, given parliament is clogged up with Brexit.

By then, BDO and other challengers will have taken on more partners to cope with joint audits and grown their IT investments, MacGregor said.

The CMA is clever in granting companies an exemption from joint audits if they hire a challenger as a sole auditor, MacGregor said. "We know we will be contacted by a lot of people who want us to take over as sole auditor," he said.

(Reporting by Huw Jones; Editing by Mark Potter)

By Huw Jones