The head of the UK accounting regulator has asked for the 'invisible barriers' claimed to be blocking entry to the audit market to be made 'visible' in efforts to reform the market.

Paul Boyle, chief executive of the Financial Reporting Council, said: 'If there is anyone out there that still feels these exist, then I would like them to please [come forward].'

Boyle was commenting on the final outcome of the FRC's consultation on choice in the audit market, in which mid-tier firms repeatedly referred to 'invisible barriers', or prejudices, that made it difficult for them to break into the large audit market.

The FRC formed a Market Participants Group, made up of investors, accountants and company FDs, who sifted through hundreds of suggestions as to how best to widen choice in the UK audit market.

During this time, BDO managing partner Jeremy Newman was particularly vocal over how 'invisible barriers' continued to exist to prevent firms below the Big Four entering the market.

Last month, Newman said: 'We continue to struggle to secure audits from the FTSE 350… this is not about our scale or competence, but is evidence that there are invisible barriers preventing us, and others, from entering the market.'

This week Newman said the invisible barriers are built around prejudice and preconceived views. 'They [the MPG] could have done something about Big Four clauses in banking agreements, in which only a Big Four firm can be appointed.

'One way to knock out the prejudice would be to not permit the clauses,' he said.

Boyle said the FRC had not said there are no barriers to the mid-tier firms.

'There are a whole series of barriers to firms outside the Big Four and those are the ones identified in the MPG's report. And all the recommendations are in effect about reducing one or other of those barriers.

'What I struggle with is what other barriers are there? There has been plenty of opportunity for people to write to us to draw our attention to these.'

The MPG also recommended that boards disclose any 'contractual obligations to appoint certain types of audit firms'.