Southwark Crown Court last month heard that road worker George Ball, 58, was using a Stihl petrol-driven cut-off saw to cut tree roots and branches while clearing a drain but it was fitted with an inappropriate blade, which became stuck. When he pulled it free, the blade ran across the top of his left knee, damaging ligaments and cartilage and requiring 60 stitches.
An investigation carried out by the Health & Safety Executive into the incident, which happened in March 2015, also found that no risk assessment had been conducted for the work and that a risk assessment for the saw's use failed to cover cutting branches.
The fine is one of the first to be imposed on a local authority since the new sentencing guidelines for health and safety offences were introduced earlier this year.
A representative for the borough said: "The council pleaded guilty in this case and accepts that it was at fault for this accident. However, the council is considering an appeal in respect of the level of fine imposed by the court."