Hounslow Council has written off nearly a third of the council tax it was owed, new figures show - the highest rate in England.
Civic Centre bean counters gave up chasing £9.1m, or 31.7 per cent, of the council's historic arrears last year.
During the same period, they collected £3.7m which was owed from 2012/13 or before, according to figures published last Thursday (July 3) by the Department for Communities and Local Government.
Despite the huge write-off, the council's total arrears stand at £21.4m.
That means on average each household in the borough owes £219 - the 16th highest figure in the country, albeit an improvement on Hounslow's fourth position last year.
Councillor Theo Dennison, Hounslow's cabinet member for finance, said: "Local council tax payers should be reassured that we have not written off any debt that should, and will, be collected.
"The amount of bad debt written off last year reflects an accumulation of uncollectable arrears – due to deaths, insolvency and the like – going back more than 20 years.
"Last year, we carried out an exercise to rationalise this debt for the first time, and wrote off the debt we know is definitely unrecoverable. These are cases such as where the debtors are deceased or insolvent and there is no legal means for us to recover that money. This has left us with a more accurate record of the debt owed to us, which we will continue to pursue until it is repaid.
"Last year, the amount of recoverable debt collected rose to 19.0 per cent, up from 15.6 per cent the previous year - almost double the level for 2008/9 of 10.5 per cent. We will continue to pursue people for any monies owed, and will take whatever action necessary – up to and including prison as happened in one case last year.
"We know that some people have financial difficulties, and if they are unable to pay their council tax they should not ignore it, and should contact us as soon as possible to see what support we can offer.”
Council tax collection rates in the borough fell significantly last year, from 97.8 per cent in 2012/13 to 96.7 per cent, which is well below the national average of 97.8 per cent.
These are the first figures to be released since the Government introduced major changes to the council tax benefit system in April last year.
A reduction in central government funding means all working age claimants in Hounslow must now pay at least 8.5 per cent of the total bill, even if they had previously paid nothing.
Hounslow was not the only west London council to write off a large chunk of its arrears last year. Harrow scrubbed off 20.8 per cent and Brent 18.8 per cent of the money they were owed from 2012/13 or earlier.