taxation expert George Rozvany, the Big Four are "the masterminds of multinational tax avoidance and the architects of tax schemes which cost governments and their taxpayers an estimated a year". At the same time they are advising governments on tax reforms, they are advising their multinational clients on how to avoid taxes. Market concentration and alleged collusion amongst the Big Four In the wake of industry concentration and the occasional firm failure, the issue of a credible alternative industry structure has been raised. The limiting factor on the expansion of the Big Four to include additional firms, is that although some of the firms in the next tier have become quite substantially large, or have formed international networks, effectively all large public companies insist on having an audit performed by a Big Four network. This creates the complication that smaller firms have no way to compete well enough to make it into the top end of the market. Documents published in June 2010 show that some UK companies' banking covenants required them to use one of the Big Four. This approach from the lender prevents firms in the next tier from competing for audit work for such companies. The British Bankers' Association said that such clauses are rare. Current discussions in the UK consider outlawing such clauses. In February 2011, the Irish Director of Corporate Enforcement Paul Appleby said that auditors "report surprisingly few types of company law offences to us", with the so-called "big four" auditing firms reporting the least often to his office, at just 5% of all reports. In 2011, the House of Lords of United Kingdom completed an inquiry into the financial crisis, and called for an Office of Fair Trading investigation into the dominance of the Big Four. In September 2019, Bloomberg News reported that The Big Four controlled 95% of the FTSE 250 audit market by client numbers and 96% by market capitalization in August 2019, according to Adviser Rankings. In 2018, an Australian parliamentary committee was told that the heads of the Big Four firms have met regularly for dinner. The revelation was among issues which led to an inquiry by the Australian Competition & Consumer Commission into possible collusion in the selling of audit and other services. However, Ernst & Young told the inquiry that the dinners, which were held once or twice a year, were to discuss industry trends and issues