Perhaps the most striking feature of the service lines in this year’s Top 50 is the subdued growth in audit. Audit has grown by only 4.8% according to this year’s survey, compared with double-digit growth for other lines of work.

Excluding Deloitte (which submitted the same figures for this year as it did for last year), overall the firms made £2.83bn this year, compared with £2.7bn last year.

For comparison purposes only, firms in the Top 50 in 2007 and 2008 were measured. The total audit fee income this year is £3.42bn across the whole of the Top 50.

Tax revenues were up by 12%, again excluding Deloitte, from £1.75bn to £1.95bn. Total tax revenues for the Top 50 is £2.46bn.

Grant Thornton’s external head of professional affairs Steve Maslin says he is not surprised at the growth in other sectors because of significant expansion in the economy. ‘There has been a large degree of corporate finance activity and, to some extent, consulting and tax work on the back of that activity,’ he says. ‘As we come into the current year, I would suspect that an awful lot of those other service line growths are likely to slow as there has been a downturn in discretionary spending consulting and there is likely to be a fall in a number of substantial new flotations.’

Maslin says that when looking at the audit numbers bear in mind that different firms include different items in what they report on in different service lines. ‘Some of what is disclosed might also be included in transaction support work, and some of those classifications might move from one year to another, and these would impact on growth across service lines.’

Deloitte’s head of assurance, Martyn Jones, says the audit figures also reflect the tail-end of the impact of the change to guidance relating to Sarbanes-Oxley. ‘The audit market revenues reflect a number of regulatory developments, along with upcoming accounting developments, all of which will impact audit costs.

Clearly, through the credit crunch there is a great need in many cases for more work arising from additional efforts in valuation and going through certain issues.’

He adds: ‘Increasingly, when you stand back and look at the revenue audits of large companies, you find they are driven by regulatory change, and every time new standards or others are issued, it has an impact on the cost of audit.’