Clifford Chance's (CC) partners increased their pro bono contributions by 31% last year, with the firm as a whole investing hours valued at a total of £17.8m in pro bono work during 2010-11.

The figures are contained within CC's annual corporate responsibility report, which states that the magic circle firm invested a total of 58,368 hours in pro bono and community activities during the year, up 2% from the figure of 57,071 hours reported last year.

The report also states that the average number of pro bono hours recorded by all partners was 12 – a figure the firm claims marks a 31% increase on the hours partners contributed during 2009-10.

The report also provides a breakdown of diversity statistics at the firm, offering an indication of the gradual progress being made on female promotions and ethnic diversity within its lawyer and support staff ranks.

CC has stated a long-term intention to reach 30% female representation in its partnership, and last year matched this target with women comprising 30% of the firm's 2011 partner promotions.

However, the overall proportion of female partners at the firm remained static at 14.5%, although representation among its lawyer ranks rose marginally from 48% to 49%.

Meanwhile, the percentage of London partners self-reporting as coming from an ethnic minority increased from 2.6% to 5.4%.

CC last year became one of the first firms to place a value on its aggregated pro bono efforts, when it reported 2009-10 pro bono hours worth an equivalent of £17m in billable hours.

The magic circle firm's accounts for 2010-11 also show that staff costs rose marginally from £535m to £537m over the year, while other operating costs decreased from £327m to £300m.

During 2010-11 the firm also improved its cash position by £44.4m to £64.5m, paid off a bank borrowing facility of £92m, and renegotiated a new bank facility which is due to expire in 2016.

In addition, CC stated that it had used up the £25.7m fund it set up at the end of 2003 as a reserve for exceptional costs. The majority of this fund was used to pay for the firm's extensive restructuring during the financial downturn which saw it reduce its global partnership by 15%.

A spokesperson said: "Following the introduction of new accounting rules, the firm changed its accounting policy at the end of the 2003 financial year. This created a one-off gain that was credited to a reserve. Over the intervening period, this reserve has been used to help fund certain exceptional costs e.g. the restructuring of the firm's partnership. At the time of the restructuring, we explained that our reserves would be deployed in this way. This reserve has now all been spent."

The spokesperson added: "The firm's robust financial position has enabled us to successfully negotiate new borrowing facilities. These will run till 2016."