The UK accounting regulator has made its study into choice in the audit market available to the US government, after Stateside regulators surprised the market by announcing their own review into the dominance of the Big Four.

Henry Paulson, US Treasury Secretary, disclosed the move last week. The announcement has caused some confusion among firms, who are uncertain how seriously they should take the move.

Paul Boyle, chief executive of the Financial Reporting Council, said he was pleased that the US decided to launch the study officially: ‘The issue of auditor concentration is one that has global dimensions to it.’

Paulson has tasked former SEC chairman Arthur Levitt and former SEC chief accountant Donald Nicolaisen with co-chairing the committee conducting the assessment.

In the UK, Mazars was set to send out letters to the chairmen of the 500 largest companies in the UK this week to push the firm’s audit credentials. The letter campaign follows similar moves from BDO Stoy Hayward, who wrote to 100 top finance directors requesting meetings.