Productivity at the Paris arms of US law firms is racing ahead of UK rivals, according to a new survey of the competitive French market, which shows that US partners bring in almost €600,000 (£404,220) more than their English counterparts.

The research by French publication Decideurs shows that average billings-per-partner at the local arms of US practices averaged €2.22m (£1.49m), compared with €1.65m (£1.11m) at UK firms.

The gap is also evident in the average revenue-per-fee earner figures, another key measure of productivity, which shows fee earners at American practices brought in €476,880 (£312,274) against €355,500 (£239,500) at English practices.

In total, there are 22 US firms ranked in Decideurs' Top 100, generating a combined income of €501.5m (£337m) with 17 ranked English firms generating €525m (£353m).

Last year, the top 100 independent French firms employed 4,288 fee earners, with the local arms of US and UK practices employing 1,054 and 1,363 fee earners respectively.

The figures confirm the progress that US firms have made in Paris after two years in which some of New York's leading practices have attracted a number of top French lawyers and secured a string of key instructions.

Among 2004′s French-originated headline deals was the €55bn (£37.3bn) Sanofi-Synthelabo/Aventis merger, the €3.7bn (£2.6bn) acquisition by a Clayton Dubilier & Rice-led consortium of Rexel, the largest leveraged buy-out in Europe last year, and France Telecom's €3.9bn (£2.6bn) takeover of Wanadoo. The three deals generated lucrative roles for New York trio Cleary Gottlieb Steen & Hamilton, Debevoise & Plimpton and Sullivan & Cromwell respectively.

However, the top 100 table was led in revenue terms by domestic giants, with Fidal in the top spot generating revenues of €250m (£169.3m), Gide Loyrette Nouel second with €125.6m (£85m) and EY Law's local arm third with €114m (£77.2m), showing that French practices continue to dominate the mid-market.

US firms to post strong growth in revenue included 11th-placed Latham & Watkins (+36.8%), 13th-placed White & Case (+44.8%), 19th-placed Jones Day (+38.1%) and 46th-placed Mayer Brown Rowe & Maw (+26.1%).

Mayer Brown senior Paris partner Jean-Pierre Lee told Legal Week: "Our growth has been down to the addition of some talented laterals, such as Xavier Jaspar [from EY Law] who brought an excellent book of business in the private equity sector."

Latham's Paris managing partner Olivier Delattre commented: "Four or five years ago the model of US firms was mainly focused on corporate and finance work, but we are also seeing some changes in the market.

Firms like Jones Day, White & Case and Shearman & Sterling are now moving into full service practice."

However, some US rivals recorded negative growth, including Baker & McKenzie(-5.3%),Paul Hastings Janofsky & Walker
(-10.4%) and,most dramatically, Orrick Herrington & Sutcliffe
(-19.9%).

In some cases, the Paris practices of leading London firms saw a fall in revenue, including Freshfields Bruckhaus Deringer, which was the top-ranked English firm in 6th place. Other London

firms to see falls included Lovells, Herbert Smith, Slaughter and May, Simmons & Simmons, Norton Rose and Denton Wilde Sapte.

UK rivals to increase fee income included Clifford Chance (7th), Linklaters (8th), Allen & Overy (18th), Ashurst (25th) and Bird & Bird (44th).

The four firms with the sharpest falls in growth were all French and included respected practices De Pardieu Brocas Maffei, Veil Jourde and Bignon Lebray & Associes.