Three-quarters of top-100 law firms have been approached by other firms with a view to merging this year, new research has suggested.

However, a fifth of firms unsuccessfully tried to complete a merger over the past year, according to a survey by accountancy and financial services group Smith & Williamson.

The greatest level of merger activity was predicted by firms in the mid-tier, with 83% of firms with between 50 and 99 partners expecting law firm mergers to increase.

In 2008, 60% of top 100 firms expected an increase in law firm mergers, while in 2007, 49% expected an increase.

Giles Murphy, director at Smith & Williamson, said: ‘The list of the top-100 law firms could start to take on a significantly different look. This [research] suggests that behind-the-scenes discussions regarding mergers and acquisitions are a regular feature in the legal community.’

Some 82% of firms cited differences in culture as a problem area for mergers, with 58% saying integrating systems was as big a potential difficulty.

A quarter of firms that acquired teams from other firms took on 20 or more individuals at once. Six in 10 law firms with more than 100 partners acquired a team of two or more lawyers from another firm in the past year.

Managing partners and financial directors from 121 firms were surveyed this autumn, including 59 firms in the top 100, of which ten were in the top 20 and 31 were in the top 50.