Elon Musk's Twitter was hit with a yellow card from the European Commission on Thursday as its reported efforts to tackle disinformation fell short of those by Alphabet's Google, Meta Platforms, Microsoft and TikTok.

The companies presented progress reports on compliance with a beefed-up European Union (EU) code of practice on disinformation in the last six months.

The reports included data on how much advertising revenue the companies had averted from disinformation actors, the number or value of political advertisements accepted or rejected and instances of manipulative behaviours detected.

The European Commission last year linked the code to new online content rules known as the Digital Services Act which allows regulators to fine companies as much as six percent of their global turnover for breaches.

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Commission Vice-President for Values and Transparency Vera Jourova singled out Twitter for criticism.

Twitter did not immediately respond to a request for comment.

"I am disappointed to see that Twitter's report lags behind others and I expect a more serious commitment to their obligations stemming from the Code," Jourova said in a statement.

The EU executive said Twitter's report lacked data and did not contain information on commitments to empower fact-checkers.

EU industry chief Thierry Breton warned of hefty sanctions for non-compliance.

"It is in the interest of all signatories to abide by their commitment to fully implement the code of practice against disinformation, in anticipation of the obligations under the Digital Services Act," he said.

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Activist NGO Avaaz said Big Tech was falling short.

"The circus at Twitter is undermining the very foundations of the code. They've set the bar so low that nobody's looking at the failures of other platforms," its campaign director Luca Nicotra said.

"Google's made zero progress in collaborating with fact-checkers and is really behind on transparency and access to data. TikTok is trying to catch up but its algorithm is still massively accelerating disinformation. Despite some progress, Meta's sheer size means they're often still one of the biggest sources of disinformation," he said.

Google said it was committed to making the code a success. Meta said it had invested heavily in its efforts and that its teams continue to work to improve its approach. TikTok said in a blog post that it will ramp up its efforts.

The next reports are due in July. The signatories to the code on Thursday launched a transparency centre allowing EU citizens, researchers and NGOs to access online information about their efforts in combating disinformation.

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