The findings, described as "shameful" by the society's president, Tony Girling, will come as a serious embarrassment to a profession that has preached a strong message of equality and into which women are now entering in greater numbers than men.
Speaking on the first day of the Law Society's annual conference in Manchester, Mr Girling, told delegates: "How can anyone conceivably stand up and argue in this day and age that equality of talent does not justify equality of treatment?
"There are problems about partnerships - career breaks and all that - some may say. But surely those women who have made it to be partners or assistant solicitors are entitled to equal reward with their male colleagues. That isn't what is happening."
Taking median earnings. The raw data from the survey shows male assistant solicitors earning pounds 24,000 compared with pounds 21,000 for women. At the level of salaried partners, men are earning pounds 37,000 compared with pounds 32,000 for women. Among equity partners, the gulf widens to pounds 51,000 for men and pounds 36,000 for women.
Mr Girling said afterwards that even when the figures were adjusted for factors like size and location of firm, age and length of qualification, there was still an average difference of pounds 1,700 between male and female associate or assistant solicitors. "That is a lot of money," he said.
Mr Girling was giving advance warning of the findings which are part of a survey of solicitors' incomes to be published next month. The ongoing study, by Coopers and Lybrand and Scantel, is examining 579 representative firms of up to 80 partners, thus excluding the very top earners in City firms.
The exercise is the society's first-ever investigation into solicitors' take-home pay as opposed to profitability.
Mr Girling agreed that women solicitors appeared to be being exploited. "I feel ashamed," he said. "It continues to indicate that solicitors do feel that women are people they can get away with paying at lower levels."
A third of the 66,123 practising solicitors in England and Wales are women, and slightly more than 50 per cent of each year's new intake are female.
Solicitors found guilty of breaching a professional practice rule against discrimination, could be disciplined for misconduct. But Mr Girling said it was "very much a question of education, encouragement and exhortation".
Studies carried out for the society by the Policy Studies Institute also show that people from ethnic minorities face considerable difficulty in getting training contracts to complete their qualification as solicitors.Reuse content