While the highest-paid English solicitor earns pounds 700,000 a year, the top earners in America are on pounds 2.2m and can expect more generous bonuses.
The study, compiled by the magazine Legal Business, shows that although UK solicitors' practices hold their own in terms of international presence, the most profitable UK firm, Slaughter and May, is ranked only ninth in the world in terms of profits per partner. Even partners at Clifford Chance, which recently became the largest law firm in the world, are paid pounds 575,000. The highest-earning US lawyers - at Robins, Kaplan, Miller & Ciresi in New York - earn pounds 2.2m a year.
The pay differential between Britain and the United States is partly the result of an isolationist approach to international law by some American firms. Some of the New York law firms see no need to broaden their client base outside the US when they have such a lucrative home market. The top British firms take the opposite view and are consolidating their dominance in Europe with mergers with German firms. This is a costly strategy, and for the short term is holding profits back at the British firms.
But the pay gap is one reason why American law firms are having no trouble poaching top partners from City firms.Earlier this year, an American firm advertised the first pounds 1m pay packet. Last month a survey of law firms in London showed that British graduates were being offered starting salaries of pounds 66,000 by the Americans - double what English law firms pay their newly qualified lawyers.
Gill Jones, a consultant at Taylor Root who carried out the survey, said the real starting salaries at American law firms were even higher because New York firms in London also paid pounds 5,000 annual bonuses.
Some English law firms are now forced to pay their lawyers bonuses in the same way the big banks have been doing for many years.
Many English firms expect their trainee lawyers to start on fairly low salaries and work their way up the firm. Using the "lock-step" system, English solicitors are paid a fixed amount from the pooled income of the practice in proportion to the number of years they have been a partner at the firm. Bonuses and paying lawyers for what work they bring in to the practice is anathema to English solicitors.