The number of audit firms registered to carry out statutory audit work in the UK and Republic of Ireland (ROI) fell by 4.7% in 2017/18, down from 5,660 to 5,394 audit firms, according to research by the UK’s Financial Reporting Council (FRC).

This was is in part due to a decline in both the number of sole practitioner audit firms (down from 2,733 to 2,558) and firms with 2 – 6 principals (down from 2,618 to 2,534).

The research was reported in the FRC’s latest edition of Key Facts and Trends in the Accountancy Profession.

It also highlighted that since the last report, the Big Four have increased their share of the UK audit market with 100% of the FTSE 100 companies now being audited by a Big Four firm.

The research found that the Big Four increased their combined total fee income by 4.7% to £10.95bn and audit fee income by 1.7% to £2.1bn. By contrast, total fee income at non-big four public interest entity audit firms fell by 8.1% and audit fee income fell by 6.3% (compared to a 3% increase in 2016/17).