Global action is required to tackle the web's "downward plunge to a dysfunctional future", says its inventor Sir Tim Berners-Lee.

He made the comments in an interview to mark 30 years since he submitted his proposal for the web.

Sir Tim says people have realised how their data could be "manipulated" after the Facebook and Cambridge Analytica scandal. However he also feels problems such as data breaches, hacking and misinformation can be tackled.

In an open letter, the web's creator acknowledges that many people doubt the web can be a force for good.

He has his own anxieties about its future, saying: "I'm very concerned about nastiness and misinformation spreading.

"When the Cambridge Analytica thing went down [people] realised that elections had been manipulated using data that they contributed."

He says he feels people are beginning to better understand the risks they face as web users, but adds that in recent years he has increasingly felt that the principles of an open web need to be safeguarded.

In his letter, Sir Tim outlines three specific areas of "dysfunction" that he feels are harming the web today: malicious activity such as hacking and harassment; problematic system design such as business models that reward clickbait; and unintended consequences such as aggressive or polarised discussions.

These things could be dealt with, in part, through new laws and systems that limit bad behaviour online, he claims.

He also spoke about the Contract for the Web project, which he helped to launch late last year.

"We need open web champions within government - civil servants and elected officials who will take action when private sector interests threaten the public good and who will stand up to protect the open web," he wrote.

He talked about what had happened since he submitted his proposal for the web 30 years ago - described by his boss as "vague but exciting" – and that in the last few years he has realised it is not enough to just campaign for an open web and leave people to their own devices.

Berners-Lee has a plan - the Contract for the Web - to put things back on the right track but it depends on governments and corporations doing their part, and the citizens of the web pressing them to act.

When asked if he thought the overall impact of the web had been good, he said that after a good first 15 years, things had turned bad and a "mid-course correction" is needed.