Football clubs are employing cybersecurity firms to scour players' social media accounts
The clubs are looking for evidence of "bigotry, hate speech, and other illegal offensive behavior," according to the report.
Private investigation and cybersecurity firm Kroll has a list of 1,000 "problematic words" it looks for when trawling football players' Facebook, Twitter, Instagram, and other social media accounts.
The company said it is working with "several" Premier League and Championship clubs.
Kroll managing director Ben Hamilton told The Guardian: "We're looking for any sign of instability. Anything that could damage the reputation of a club, whether that's extreme promiscuity, or religious or extremist beliefs. British examples might include the National Front, any anti-Jewish organisation, [the] English Defence League, different words that relate to fascism or suicide bombers, [or the terms] Muslim, Catholic, Republican, pikey, Gypsy."
Cybersecurity firms are also flagging up any references to drug use, racist terms, and evidence of criminality.
Hamilton said if concerns about a player's social media activity were serious enough, Kroll could go to court to get access to their private messaging accounts, such as Snapchat or WhatsApp.
Several players - including former Manchester United and Queens Park Rangers player Rio Ferdinand and former Chelsea defender Ashley Cole - have been fined by the Football Association for using offensive terms on social media.
Last month, former Sunderland footballer Adam Johnson was jailed for six years for grooming and sexual activity with a 15-year-old schoolgirl. Evidence in the case included messages and images sent over social media and messaging apps including Snapchat and WhatsApp.