Britain wants to take a world-leading role in regulating the biggest tech companies.

The UK government says it wants to legislate for a new independent regulator that would oversee "harmful content" on social media, search engines, messaging, and file-sharing platforms.

It would be the UK's first time regulating online safety, with the internet conventionally seen as ungovernable.

Platforms that fail to keep hate speech and content relating to sexual abuse, violence, terrorism, or self-abuse off their services would face huge fines under the proposed rules.

Industry lobbying bodies representing Facebook, Google, and other big tech firms say the proposed laws are too vague and may harm competition.

The internet's days as the Wild West may be numbered.

The British government has laid out a blueprint for groundbreaking new laws that would regulate social media, search, messaging, and even file-sharing platforms for content found to cause "online harm." That umbrella term includes content relating to sexual abuse, violence, hate speech and terrorism, self-harm, and underage sexting.

The proposals, dubbed the world's "first online safety laws" in an emailed statement, coincide with global pressure on US tech firms to prevent terrorist propaganda, hate speech, and depictions of self-harm from appearing on their sites. It also comes at a time when Silicon Valley leaders like Mark Zuckerberg are calling for regulation.

Facebook, YouTube, and the more niche 8chan came in for severe criticism just last month when the Christchurch, New Zealand, attacker livestreamed the shootings at two mosques. In February, Instagram banned "extreme" images of self-harm after the suicide of the British teenager Molly Russell.

Read more: Facebook, YouTube, and Snapchat execs could be named, shamed, and held personally liable for harmful content under new UK laws

The proposals, put forward in a white paper by the UK's Department for Digital, Culture, Media and Sport, call for a new independent regulator that would police these platforms for harmful content.

It will have the power to issue major fines and even hold individual executives responsible for failing to comply with any new laws. Fines could reach billions of dollars for the biggest companies, Culture Minister Margot James told Business Insider in February.

Tech firms would also need to obey a "duty of care," which would require them to take steps meant to keep users safe and to deal with illegal or harmful content.

Other proposals include:

Forcing social-media firms to publish transparency reports about content considered harmful on their services and the measures they take to combat it.

Compelling companies to respond quickly to user complaints, possibly akin to Germany's controversial "NetzDG" law.

Codes of practice that might require tech firms to minimize the spread of misinformation during elections.

A framework to help tech firms build safety features into their apps from the start.

A media-literacy strategy to help people recognize misinformation and malicious behaviors.

"The internet can be brilliant at connecting people across the world — but for too long these companies have not done enough to protect users, especially children and young people, from harmful content," British Prime Minister Theresa May said in a statement.

"That is not good enough, and it is time to do things differently. We have listened to campaigners and parents, and are putting a legal duty of care on internet companies to keep people safe. Online companies must start taking responsibility for their platforms, and help restore public trust in this technology."

Big tech wants more detail about how the new laws will actually work

The proposals are still some way off becoming legislation, and what actually ends up becoming law may look quite different from Monday's policy paper after further industry and public consultation.

Facebook CEO Mark Zuckerberg. Getty

The Internet Association, a lobby group that counts Facebook, Google, Snap, Reddit, and Twitter among its members, said the proposals needed tightening up.

"The internet industry is committed to working together with government and civil society to ensure the UK is a safe place to be online," the Internet Association's UK executive director, Daniel Dyball, said in a statement. "But to do this, we need proposals that are targeted and practical to implement for platforms both big and small.

"We also need to protect freedom of speech and the services consumers love. The scope of the recommendations is extremely wide, and decisions about how we regulate what is and is not allowed online should be made by Parliament."

Coadec, a group that lobbies on behalf of startups, said overly strict regulation could punish smaller firms that don't have the money and clout of Facebook and Google.

"Everyone, including British startups, shares the goal of a safer internet — but these plans will entrench the tech giants, not punish them," Coadec's executive director, Dom Hallas, said.

"The vast scope of the proposals means they cover not just social media but virtually the entire internet — from file sharing to newspaper comment sections. Those most impacted will not be the tech giants the government claims they are targeting, but everyone else. It will benefit the largest platforms with the resources and legal might to comply — and restrict the ability of British startups to compete fairly."