We thought technology products would always be a force for good. We were lured by their convenience and ease of use; by the idea of free access to everything and everyone.

We did not see the dark side - until it was too late. By then we were already addicted, with horrific consequences for public health, democracy and the economy.

Smartphones are valuable, but the apps delivered on them are the technological equivalent of sugar: easy to consume to excess.

Internet platforms apply the techniques of propaganda or gambling to trigger emotional responses over which users have little or no control. Technology companies are running an uncontrolled psychological experiment on billions of people.

In a perfect world, the makers of smartphones and apps would recognise the harm they have caused and take remedial action. With only a few small exceptions, they have not done so.

In the pursuit of profit, Internet platforms are mounting an assault on the minds of children. Governments, educators and parents must step up to address this crisis.

Advertising-supported platforms should be regulated in the same way as alcohol and tobacco, with age restrictions and warning labels.

YouTube Kids has become a wasteland of age-inappropriate videos, stimulating children in ways that make the real world seem boring.

While Google has removed huge amounts of age-inappropriate content from YouTube Kids, it has not taken adequate precautions to prevent the posting of such content. YouTube has also become the place for recruiting and training extremists.

Facebook recently introduced Messenger Kids, a texting service whose primary function seems to be to train children for a life lived within its product ecosystem.

For adolescents, Instagram has become a weapon for psychological bullying.

Advertisers themselves are starting to recognise the problem and some are taking action. Unilever last week announced it would withdraw ads from platforms that "create division in society, and promote anger or hate". Platforms such as Google and Facebook must take steps to "protect our children" the company said.

Western democracies need a co-ordinated response to the manipulation of their populations by hostile powers. Facebook alone is used by more than two billion people.

In a world of limitless access to information, disinformation is spreading rapidly. Google's search results can be gamed with conspiracy theories and nonsense. Facebook exploits its users' fear and anger to such a degree that many are vulnerable to manipulation by those who exploit its algorithms and architecture to undermine democracy and harm the powerless.

The crisis we face today is the result of bad incentives created by advertising business models, poor judgment by the executives in charge and ineffective regulation.

About one-third of the world's population owns a smartphone, and many owners check their phones a frightening number of times a day, often from the moment they wake until the moment they go to bed.

Not all users of Internet platforms are addicted, but the 1.3 billion people who use Facebook every day are psychologically attached to it to a degree.

Even if they could break the attachment, those users are at the mercy of big corporations whose data archives rival those of the best intelligence services, and whose terms of service confer no meaningful rights to the owners of that data.

Big Tech companies insist they should be allowed to regulate themselves. Unfortunately, their record on this point is dreadful.

For example, the response of Facebook, Google and Twitter to evidence of interference on elections has been to deny, delay, and dissemble. Their proposed "fixes" have been inadequate.

Facebook and Google have grown so large and powerful that new approaches to regulation may be required. The European Union's Global Data Protection Regulation (GDPR) is an important step in the right direction, particularly with respect to privacy and data rights. Unfortunately, the EU's enforcement mechanisms will need an upgrade if they are to deliver on the promise of GDPR.

Restoring privacy and data rights in the EU would be a huge step forward, but there needs to be many more steps. We need to repair democracies in Western Europe and North America. We need to protect children from technology that stunts their emotional development. We need to protect adults from interruptions by endless notifications and apps that compete with their sleep.

We need to protect economies from the monopolistic behaviour of Internet platforms, which has already produced lower rates of innovation and start-up formation.

Unlike a year ago, the threat from the Internet platform companies is a topic of conversation across the developed world. The next step is to convert talk into action.

FINANCIAL TIMES

• The writer is a venture capitalist and was an early investor in Facebook and Google.