The Duke and Duchess of Cambridge have joined a nationwide boycott of social media over online racism and abuse linked to sport.

William and Kate are backing football clubs, players and other sporting bodies in a four-day absence from Twitter, Instagram and Facebook.

The couple had planned to share content online over the weekend to mark their daughter Princess Charlotte’s sixth birthday tomorrow.

The aim of the protest – revealed in Sportsmail – is to persuade the tech giants to take a stronger stance against racist and sexist abuse by users of the platforms.

The future king tweeted the decision yesterday on his official Kensington Royal Twitter feed, saying: ‘As President of the FA [Football Association] I join the entire football community in the social media boycott this weekend. W.’

Earlier this year William, 38, also spoke out after a number of high-profile black players condemned the racist abuse they had received online.

‘Racist abuse – whether on the pitch, in the stands, or on social media – is despicable and it must stop now,’ he said. ‘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.’

It is not the first time that the prince has taken a strong public stance towards the major tech firms.

He set up a taskforce to tackle cyberbullying in 2016, but two years later conceded the initiative had failed to persuade social media giants such as Facebook to co-operate.

In an unprecedented intervention, he condemned the ‘defensive’ attitude of social media companies in refusing to accept their role in the spread of hate speech, fake news and online bullying.

He said: ‘I am very concerned though that on every challenge they face – fake news, extremism, polarisation, hate speech, trolling, mental health, privacy, and bullying –our tech leaders seem to be on the back foot.

‘The noise of shareholders, bottom lines, and profits is distracting them from the values that made them so successful in the first place.’

The online boycott began at 3pm yesterday and will end at 11.59pm on Monday.

It has been led by the football community, with top players such as Manchester City and England star Raheem Sterling taking part.

Formula One’s Lewis Hamilton announced his boycott and the bodies for rugby union, rugby league, cricket, cycling, horseracing and the Lawn Tennis Association are also involved.

The Premier League promised that it would not stop challenging companies ‘until discriminatory online abuse is removed from our game and wider society’.

Manchester United revealed last week that there had been a 350 per cent increase in abuse directed towards the club’s players. It found 86 per cent of those posts were racist, while 8 per cent were homophobic or transphobic.

Facebook, which owns Instagram, has previously said it is ‘committed’ to tackling abuse on its platforms.

Twitter has said it is ‘resolute in our commitment to ensure the football conversation on our service is safe for fans, players and everyone involved in the game’.

The company added it had removed more than 7,000 football-related tweets in the UK that violated its rules.