The survey also found that more than two-thirds of lawyers would take a cut in salary in exchange for a better balance between work and outside life, compared with just a quarter in the national average.
The consultancy's chief executive, Liz Bargh, comments: "This will hit a nerve with many people; these are highly capable professional people keen to give the outward appearance of keeping control. Yet the sacrifices some are making for the sake of their careers are shocking."
The life of a young City lawyer in the Nineties has become more like the life of a City trader during the booming Eighties. Many solicitors are happy now to sell themselves to clients as superlawyers who can go days without sleep to complete a deal or win a case. The work-hard culture in some law firms means that lawyers will even compete with each other to leave the office last. Stories abound of solicitors keeping computers switched on all night just to give the impression that they are still in the building.
And figures compiled recently by the personnel departments of some of the leading City law firms show that stories of overworked lawyers are not apocryphal; the firms are struggling to hang on to assistant solicitors. Turnover rates among the worst affected firms are as much as 40 per cent. Many are falling victim to burn-out and high levels of stress.
The City's largest firm, Clifford Chance, now operates an in-house stress- counselling service for those lawyers who may have done one deal too many. A managing partner, Tony Williams, whose own firm has an assistant solicitor turnover rate of between 22 and 24 per cent, says: "We want to do our best so that people do not suffer burn-out. We want to help them manage the level of work they can handle."
But he acknowledges that the top 10 law firms are facing an exodus of young lawyers from the City. "There are high pressures in the top firms, and it is clearly an issue in relation to retaining people, but hours are not the overriding factor."
The firm now carries out extensive exit interviews of departing lawyers. These show that many lawyers are deliberately opting for different lifestyles. "Some decide they simply don't want City life. Very few go to our major competitors. The pressure issue is recognised as applying to all the major law firms, not just one or two."
Barry Pritchard, co-ordinator of Solcare, the Law-Society-funded charity for solicitors with alcohol or drug problems, says many solicitors cope with stress by becoming dependent on drugs or alcohol.
He warns that City law firms which allow their solicitors to work 36 hours without sleep are storing up trouble. "Not only are they putting the health of their lawyers at risk, they could also be running the risk of serious errors being made, which can cost big money."
Mr Pritchard advises lawyers caught up in gruelling monotonous deals to go home and grab a couple of hours' sleep. "If someone is going to carry on working non-stop for 48 hours, the quality of their work is going to be pretty abysmal."
Clifford Chance's Williams argues that because of client demands, it is difficult to ensure that lawyers can always take proper breaks during deals or major litigation. A psychologist, Dr David Lewis, has carried out a detailed comparative study of the pressures under which professionals work. It showed that only doctors and air traffic controllers experience more stressful working lives than lawyers.
Dr Lewis says that in his study, it was the assistant solicitors who experienced the greatest level of stress because they had little control over their working environment. Many felt the greatest stress came from having to justify themselves in terms of billing power, and many thought that doing "pro bono" legal work would at least provide some benefit in terms of personal satisfaction.
The ones to benefit from all this angst and burn-out have been the larger regional law firms who have been cashing in on the solicitor fall-out from the London City firms. Last year, Birmingham firm Wragge & Co tried to tempt City lawyers with an ad campaign that sold Birmingham as the place where was more quality of life. Ex-City lawyer David Barron, who is now at Wragge & Co says: "I want to be able to see people during the week and have some sort of life. At the weekend, I want to be in the countryside rather than face a two-hour slog on the motorway."
And at the Tunbridge Wells firm Cripps Harries Hall, managing partner Jonathan Denny says: ""In spite of the very high pay, there is a widespread disenchantment with the City. The pressures are excessive and people wise up to that sooner or later. But he warns that City lawyers should not regard regional practices as a soft option. "Sometimes they think they are coming for a quiet life, and they may not be working quite the same hours - but it's not going to be straight 9am to 5pm, either."
And an indication of where over-stressed lawyers may be headed in the future is in the top 10 wish-list which Management Today compiled from its survey. For lawyers, topping the list was working fewer hours, and working from home.