LONDON—Rupert Murdoch’s burning ambition to take over Europe’s profitable Sky TV and internet platform has been halted by authorities who fear that he would wield too much power and influence on British society.

The $16 billion acquisition deal has been blocked by the Competition and Markets Authority (CMA), which ruled that the merger of Fox and Sky would result in “the Murdoch family having too much control over news providers in the U.K., and too much influence over public opinion and the political agenda.”

Rupert Murdoch and his sons Lachlan and James already control Britain’s biggest selling newspaper The Sun, as well as The Times and Sunday Times through their publishing company News Corp.

Murdoch has battled for more than a decade to get his hands on the highly profitable Sky business, in which he already holds a 39 percent stake. Today, British authorities said that would not be “in the public interest.”

The Australian media magnate spent decades assiduously courting British prime ministers since Margaret Thatcher through high-level media support, secret meetings and endless personal advice. After years of cozying up to the Conservative Party, he switched his attentions to Labour leader Tony Blair when it became clear that the center-left party would sweep to power in the mid-1990s.

The relationship became even more closely entwined during the premiership of David Cameron when Murdoch deputy Rebekah Brooks was a close friend of the PM and longstanding Murdoch newspaper editor Andy Coulson was appointed as Cameron’s head of communications.

Just as Murdoch’s embrace of Downing Street appeared so tight that his ambition to takeover Sky would be waved through by the government, the phone-hacking scandal erupted and destroyed his plans.

Today’s provisional ruling could mark the end of that quest. The CMA suggests that the deal could still proceed if the Sky News network was spun off from the rest of Sky, which is a multiplatform telephone, internet, and television distribution company. Murdoch insiders had already briefed the media that the 24-hour news operation could be shut down entirely if that was the only way to secure the merger.

Anne Lambert, the chair of the CMA’s investigation, announced that the deal would not be approved unless changes were made to the structure of Sky.

“Media plurality goes to the heart of our democratic process. It is very important that no group or individual should have too much control of our news media or too much power to affect the political agenda,” she said.

Murdoch’s announced sale of Fox complicates the authorities’ findings but the investigation went ahead as the proposed deal would be completed before Disney assumed control of the media empire.

This may have been Britain’s last chance to embarrass Murdoch.

Tom Watson, the deputy Labour leader, said the ruling should be heralded as a moment to celebrate, as the country stood up to one of the world’s most power news barons.

“The Competition and Markets Authority is right to say that the Fox takeover of Sky would give the Murdoch family too much power. This is the right decision for the U.K.,” he said.

Campaigners against Murdoch had also argued that the merger should be blocked because Murdoch’s running of Fox News demonstrated that he was not committed to Britain’s tough rules on broadcasting standards, which include accuracy and a nonpartisan approach. Those complaints were not upheld.

Alex Wilks, the campaign director at Avaaz, which has led the legal fight against the merger, said: “The authorities are right to block Rupert Murdoch’s bid to take over even more of our news, which would make a mockery of the rules designed to protect the media. Now they need to expose the full extent of harassment, hacking, and pro-Trump bias at the Murdoch media empire."

In a statement, Fox said it would continue to work to find a way around the plurality ruling in time for the final verdict from the authorities in May.

“We welcome the CMA’s provisional finding that the company has a genuine commitment to broadcasting standards and the transaction would not be against the public interest in this respect,” a spokesman said.

“Regarding plurality, we are disappointed by the CMA’s provisional findings. We will continue to engage with the CMA ahead of the publication of the final report in May.”