He called on companies to withdraw their advertising from platforms that provide a ‘safe haven’ for hate and revealed he and wife Meghan have been putting pressure on business chiefs to join the tech boycott.

Writing in the US business magazine Fast Company, he said: ‘A little over four weeks ago, my wife and I started calling business leaders, heads of major corporations and chief marketing officers at brands and organisations we all use in our daily lives.

‘Our message was clear: the digital landscape is unwell and companies like yours have the chance to reconsider your role in funding and supporting online platforms that have contributed to, stoked and created the conditions for a crisis of hate, a crisis of health and a crisis of truth.’

In June Harry and Meghan joined the Stop Hate for Profit campaign, which persuaded a number of major advertisers, first in the US and later globally, to pull their spending on Facebook and Instagram in protest against the lax enforcement of hate speech policies.

In his 1,400 word article, the duke cited concerns of how the digital world will affect children — including his one-year-old son, Archie.

‘We believe we have to remodel the architecture of our online community in a way defined more by compassion than hate; by truth instead of misinformation; by equity and inclusiveness instead of injustice and fearmongering; by free, rather than weaponised, speech,’ he said.

‘Researchers I’ve spoken with are studying how social media affects people — particularly young people — and I believe the book of data that we will look back on one day will be incredibly troubling.’

The piece was slim on details for change but said there would be huge value in advertisers sitting down ‘with advocacy leaders, with policy leaders, with civil society leaders, in search of solutions that strengthen the digital community while protecting its free and open nature.’

Explaining why he was targeting advertising, he said: ‘Many of us love and enjoy social media. It’s a seemingly free resource for connecting, sharing and organising. But it’s not actually free; the cost is high.

‘Every time you click they learn more about you. Our information, private data and unknown habits are traded on for advertising space and dollars. The price we’re all paying is much higher than it appears. Whereas normally we’re the consumer buying a product, in this ever-changing digital world, we are the product.’

The couple are believed to have called more than a dozen business leaders asking them to join the boycott.

The pair have been active in campaigning against online hate speech since stepping down as senior members of the Royal Family in January, although this is the strongest intervention from either to date.

The duke and duchess are in the process of setting up Archewell, their non-profit organisation. A source told The Times that their concerns about social media would be a prominent part of this.