In the letter, 39 organisations, mostly NGOs, said big tech leaders were “seeking to mobilise the Trump administration” to protect their ability to exploit users and businesses dependent on them, while seeking to “stifle potential competitors”.

It called on the commission not to weaken enforcement of the Digital Services Act or the Digital Markets Act, two EU laws that came into force in 2022. Meta and X are being investigated under the DSA, which is intended to protect society from online harms, such as disinformation, illegal content and attempts to manipulate public opinion ahead of elections.

The Digital Markets Act was created to ensure that the biggest tech companies, including Alphabet, Amazon and Meta, do not abuse their powerful position to squeeze out potential competitors.

The EU is under pressure, as US tech billionaires position themselves close to Trump, while attacking European regulations. Meta’s chief executive, Mark Zuckerberg, derided European laws as “censorship” when he announced he was scrapping factcheckers in the US on Facebook, Instagram and Threads. Even though the measure applies only in the US, campaigners fear the spread of unchecked English-language content into Europe.

The letter said that big tech companies had already created “an unfair digital economy” that had “directly impacted the dynamism and pluralism of Europe’s economy”.

It went on: “Re-introducing contestability, fairness and choice to the digital market will already be a difficult task. If we pause or weaken enforcement, we risk making it impossible. Europe must not be bullied by the likes of Musk and Trump into weakening its DSA and DMA enforcement.”

Jan Penfrat, a co-organiser of the letter based at the European Digital Rights group, said his organisation was concerned that the commission’s legal services “might not get the political backing and the resources they need to do their job”.

“It is one thing to resist the already massive economic and lobbying power of big tech, but it is a totally different game if those companies can wield the power of the White House to try and prevent the EU from properly enforcing its own tech laws.”

The letter was also sent to two Commission vice-presidents: Teresa Ribera, who is responsible for EU competition policy, and Henna Virkkunen, who leads on DSA and DMA enforcement.

As well as NGOs, it was also signed by a handful of European tech companies and one trade union. The letter also raised concern about X’s use of algorithms to promote certain content, describing the platform under Musk as “serious threat to our democracy and political discourse in Europe”.

Earlier this month, the commission asked X to hand over internal documents about its algorithms, as it steps up its investigation into whether the social media platform has breached EU rules on content moderation.

The EU’s executive branch told the company it wanted to see internal documents about its “recommender system”, which makes content suggestions to users, and any recent changes made to it, by 15 February.

The European Medicines Agency announced on Monday it was quitting X and opening an account on Bluesky. The EMA, an EU agency based in Amsterdam, said X “no longer suits our communication needs”. The commission and other EU institutions maintain accounts on X, as officials see it as a way to reach an audience.