The planned merger between KPMG and Ernst and Young will have to be approved by competition authorities in the US, the EU, Japan, Ireland and other markets. With the authorities worldwide already examining the proposed Price Waterhouse/Coopers and Lybrand merger, there is now likely to be a thorough assessment of the impact on the industry and its clients of the two major mergers.

Regulatory approval was unlikely before March, according to Mr Colin Sharman who would be chairman of a merged KPMG/ Ernst and Young. The merger is likely to be referred to a second round of European Union regulatory scrutiny. US and Japanese regulators also have to be satisfied.

The rush to merge and expand has been driven by the globalisation of industry, with firms trying to serve international clients with all their accounting and auditing needs across the world.

But there are possible difficulties for the firms planning to merge. Mr Sharman acknowledged that client conflicts would arise. There was "a possibility" clients might take their business elsewhere if they were unhappy about being audited by the same firm as a major competitor.

One possible conflict will involve two of the world's best-known brands. Soft drinks giant Coca-Cola Co is audited by Ernst & Young and PepsiCo Inc has its books cleared by KPMG.

Between them, Ernst & Young and KPMG audit many of the world's top companies, while both Mr Sharman and Mr Land were keen to point out that their market was much deeper than just the big quoted companies.