Prince Harry, Duke of Sussex, delivered a keynote speech Tuesday at the European Parliament in Brussels, calling on social media companies to take greater responsibility for protecting children online.

His speech coincided with the launch of the "Lost Screen Memorial," an installation honouring children and young people whose deaths have been linked to online harm. Harry and his wife Megan, the Duchess of Sussex, have already launched similar memorial sites in the United States and Geneva, Switzerland.

The memorial features photographs on oversized smartphone screens and the times of death of 50 young people who lost their lives due to harm from social media.

"These are children whose futures mattered. Families whose lives have been forever changed. And a reminder of what is at stake for millions more," Harry said. "Listen to their stories. We have the knowledge, we have the technology, we have the ability to act. And no family should have to lose a child before the world decides to protect one."

During his speech in front of the Parliament, Harry highlighted the importance of the EU Kids Act, an initiative aimed at protecting minors and young adults from the negative mental effects social media can cause.

Harry stated that social media companies shouldn't put content in front of children that they wouldn't want their own children to see, and that company profit should never come before children's safety. “The majority of these companies don’t let their children on social media because they know the dangers,” he said.

He also said parents wanted better transparency in legal proceedings, as some parents who have lost a child to suicide had to wait up to eight years before they were provided access to their child's phone to find out why. "That cannot be right." he said.

Harry added that policymakers should be acting urgently to ensure children's safety is built into digital platforms from the outset, rather than becoming reactionary once harm occurs.

"We can no longer sit here and wait for thousands more children to lose their lives and millions more parents to have their children's lives changed forever," Harry said. "This whole mission has to be about safety by design. By the time things are on a phone, on an app, in a kid's hands, it is already too late."

Harry's wife, Meghan, Duchess of Sussex, accompanied him to the event but withdrew from their planned joint address over allegations against her father, Thomas Markle Sr. It was her first public appearance since her 82-year-old father was placed under house arrest in the United States last week on a charge relating to the possession of child sexual abuse material.

Thomas Markle Sr. has repeatedly called the accusations "sick lies," and both Megan and Harry declined to comment on the matter during Tuesdays event in Brussels.