Revenue at Berwin Leighton Paisner (BLP) dropped 5% to £233m, as more City firms continued to post flat results for the financial year 2012-2013.
Last year BLP, a key adviser for financial institutions, increased revenue by 7.4% to £246m.
The firm has sought to cut staff costs by around 15% this year and in May placed 100 London-based workers at risk of redundancy.
Income at City firm Travers Smith rose 3% to £86.2m in the 2012-13 financial year, while profit per equity partner (PEP) dropped 2% to £790,000.
In 2011-2012 income increased 16% at the firm to £83.8m. PEP jumped 24% to £804,000.
City firm Dentons, which was formed in March 2013 through a merger with SNR Denton, Salans and Canada's Fraser Milner Casgrain, reported a revenue increase of 1% to £829.7m and a drop in PEP of 1%.
However, revenue jumped for the second year at Mishcon de Reya, rising 13% to £88.4m. PEP rose 20% to £840,000.
In 2011-12 the firm reported revenue growth of 20% to £73.1m. PEP rose 22% to £700,000.