Match-fixing is rife at lower-level tennis events, according to a report on corruption in the sport.
The Independent Review Panel's (IRP) £20m investigation found a "tsunami" of illegal betting activity in the "lower and middle levels" of the game.
According to BBC Sport, the report uncovered no evidence of top-level players being implicated or any signs that tennis's governing bodies have attempted a cover-up.
The IRP did, however, find "some evidence of some issues" at higher-profile events such as Grand Slams, though nothing "widespread" was documented.
Internal inquiries into corruption in tennis were dubbed inadequate and the ATP has been criticised for "failing to exhaust potential leads before ending investigations".
To address the problem, the panel has made several recommendations to the ATP and the Tennis Integrity Unit about tackling corruption more effectively in the future.