Free newspapers left on trains by commuters are identified as cause of the problem by tube operator
As much as 9.5 tonnes of paper are recovered from tube trains in London every day, Tube Lines revealed in its quarterly report.
The number has more than tripled compared with past figures because free newspapers are left by commuters on trains.
The report also outlined that reliability of trains has exceeded targets by 19% because incidents that caused delay were down by 14%.
Capital expenditure at Tube Lines was also higher than previously estimated, as additional works left the investment figure at £97m instead of the £89.1m prognosis.