Britain's Prince William has called the racist abuse of footballers "despicable" and said it "must stop now", after Manchester United's Marcus Rashford became the latest victim.
William, who is the president of the Football Association, spoke out after the Professional Footballers' Association accused social media companies of being unwilling to clamp down on racist posts.
Chelsea defender Reece James, West Bromwich Albion's Romaine Sawyers and Rashford's teammates Axel Tuanzebe and Anthony Martial have all suffered online racist abuse over the past week.
Rashford was then abused after United's 0-0 draw at Arsenal on Saturday, prompting a police investigation.
"Racist abuse, whether on the pitch, in the stands or on social media, is despicable and it must stop now," William posted on Twitter.
"We all have 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.
"That responsibility extends to the platforms where so much of this activity now takes place."
The PFA called on social networks to show they were truly committed to tackling a problem it says has been "at crisis point" for two years.
"Every effort must be taken to protect them [footballers], and all other users, from racist abuse while using social media," it said.
"Offline consequences for online hate crimes must be pursued whenever possible."
Greater Manchester Police said abusive comments directed at United players had been reported and the force would be "investigating these crimes thoroughly".
Rashford, a high-profile campaigner against child food poverty, said the remarks showed "humanity and social media at its worst".
"I'm a black man and I live every day proud that I am," he tweeted. "No one, or no one comment, is going to make me feel any different.
"So sorry if you were looking for a strong reaction, you're just simply not going to get it here."
A man, 49, was arrested on suspicion of racially abusing Sawyers.
