The pro bono cause is winning widely varied support from leading firms and senior partners as research shows that many time-pressed City lawyers do not do any free legal work at all.

The latest Legal Week/ EJ Legal Big Question survey found 37% of partners do not spend any billable time on pro bono. While for some it may be a case of not counting pro bono work towards their billable hours, apparently others no longer have the time or the drive of their younger colleagues.

One corporate partner with a top 50 firm added: "I am surprised the figure is not higher.

"The main issue is a lack of time. Younger lawyers who are further down the career ladder tend not to have the family commitments that more senior lawyers have. Even after work, a lot of partners spend time meeting and greeting clients, if they are not seeing the wife and kids."

The survey revealed that 17% of respondents spent around 1% of their billable time on pro bono work, 19% spend 2% of their time. At the other end of the spectrum, 15% of respondents said they spent more than 5% of their billable time on pro bono.

Firm-wide, 26% believed that their firm spent about 1% of billable time on pro bono work, with 15% believing their firm spends approximately 2% of time on pro bono.

Trevor Cook, IP partner at Bird & Bird, commented: "Equated to turnover I expect that is a fairly realistic estimate. By definition, pro bono tends to be the smaller end of deals. However, it takes just as much work, if not a lot more."

The survey of more than 100 senior lawyers found mixed support for a US-style scheme to benchmark firm-wide commitments to pro bono.

Of those questioned, 52% said such a venture should not be launched in the UK, against 48% who backed the move.

Olswang head of tax Kay Butler commented: "I do not think such a scheme would have an impact. It is more to do with having the opportunity to do the work. The US is a much more legalistic society and there is more litigation. It is nicer for it to be left to a firm's discretion. Many UK lawyers like to do charity work that is not legal-based as well, particularly by using their contacts."

Pro bono still interests many trainees, with 59% responding that trainees sometimes enquired about the amount of pro bono work that a firm does, but 22% said trainees never asked.

One partner added: "There is a lot of under-reporting about the amount of pro bono hours we do. But some youngsters are just not as interested as they used to be. I suppose they do not have the time as they are working bloody hard anyway. The bottom line is you have to build the fees."

Interest from clients in their advisers' commitment to pro bono is mixed. Seven percent of respondents said that clients 'often' asked about the issue, compared with 48% who said client 'sometimes' asked. Forty-six percent reported no interest from clients.