The Duke of Cambridge said he is joining “the entire football community” in this weekend’s social media boycott.

The sporting world began a four-day blackout on their channels on Friday afternoon, with many players, clubs and broadcasters joining forces to say online abuse is not acceptable.

A bill on online safety is due before Parliament this year and is expected to set out a duty of care to which tech companies must adhere, with large financial penalties for those found to be in breach.

In a tweet, signed W for William, the future king pledged his support.

The post, from the Kensington Royal account, read: “As President of the FA I join the entire football community in the social media boycott this weekend. W.”

In January William hit out at racist abuse in football, describing it as “despicable” and saying it “must stop” after several black players were targeted online.

At the time, he wrote that everyone has “a responsibility to create an environment where such abuse is not tolerated, and those who choose to spread hate and division are held accountable for their actions”.

He said such responsibility “extends to the platforms where so much of this activity now takes place”.

Culture Secretary Oliver Dowden said social media giants could face multimillion-pound fines for failing to crack down on racist abuse on their platforms.

Writing in The Sun, he said: “Under the legislation, if social media companies do not keep their promises to users by, for example, failing to remove racist abuse, they will face severe sanctions.

“We could see fines of up to 10% of annual global turnover. For a company such as Facebook or YouTube, that could be billions.”

He added that the threat of enforcement would get social media companies to act.

Meanwhile, Facebook’s vice president for northern Europe Steve Hatch wrote in the Daily Telegraph that his firm has clear rules against hate speech, but “zero tolerance doesn’t mean zero incidence”.

Manchester United have revealed online abuse aimed at their players has increased 350% since September 2019.

Of 3,300 abusive posts found in an in-depth review of Twitter, Instagram and Facebook, the club said 86% were racist, while 8% were homophobic or transphobic.

The club said it had banned six fans for abusing Tottenham’s Son Heung-min online after a match earlier this month, while Chelsea announced a decade-long ban to a supporter for anti-Semitic posts.