Small but growing signs of cooperation between the right and far-right in the new EU parliament are causing concern for the center-left, which views it as a threat to the bloc's stability.

Despite far-right gains at the ballot box in June's European Parliament elections, the traditional alliance of mainstream parties kept its overall majority – and helped Ursula von der Leyen win reelection as Commission chief.

But three hard-right groups together control 187 out of 720 seats – a potent new force that von der Leyen's conservative European People's Party (EPP) group seems increasingly ready to team up with.

Officially the party line remains unchanged.

"There is no cooperation with the far-right," its leader Manfred Weber told AFP, reiterating that "the basic criteria for cooperation are to be pro-Europe, pro-Ukraine and pro-rule of law."

Likewise, the French EPP lawmaker Francois-Xavier Bellamy denied any "change of course."

"We'll defend our ideas, we'll defend our program and we'll see majorities come together around it."

In practice, though, the EPP's left-wing and centrist partners say the line is shifting.

"The alliance of right-wing forces you're seeing in several European countries is happening in the parliament too," said Younous Omarjee, a hard-left EU lawmaker and one of the parliament's dozen vice-presidents, who fears a rollback of advances on the environment and fundamental rights.

One hard-right faction, the European Conservatives and Reformists of Italian leader Giorgia Meloni, made the jump into EU governance by claiming a vice presidency in von der Leyen's new commission.

The other two are the Patriots of Europe – launched by Hungary's nationalist Prime Minister Viktor Orban – and a smaller, even more radical group called the Sovereignists.

The latter two are still being – officially – kept out in the cold by mainstream parties in tacit application of a so-called "cordon sanitaire" aimed at barring the extreme right from power.

"These two political groups definitely fall under the far-right definition," said Malta's Alex Agius Saliba, a senior lawmaker with the Socialists & Democrats. "But unfortunately it seems the EPP are not sticking with the cordon sanitaire."

'Tipping point'

Last month, the Patriots teamed up with the EPP to pass a resolution recognizing Venezuelan opposition candidate Edmundo Gonzalez Urrutia as president following the country's disputed election.

Weber defended the text as aligned with the group's longstanding position.

But, French EU lawmaker Raphael Glucksmann called the vote a "tipping point."

"From now on, in every negotiation, this will be hanging over us like a sword of Damocles," the Socialist told AFP. "The EPP will be able to say, 'If we can't find agreement with the center – we'll just make a deal with the Patriots.'"

In the same vein, Weber stands accused of seeking support from the Patriots and Sovereignists in the Conference of Presidents, the body where group leaders thrash out the parliament's political agenda.

Early this month, a meeting on confirmation hearings for new EU commissioners reportedly grew heated after the right and far-right banded together to push through their preferences.

And at this week's parliament plenary in Strasbourg, the EPP and Patriots secured the addition of a debate on preventing EU funds from being directed to terrorist movements.

Not exactly the stuff of headlines, but EU watchers see a clear pattern.

"There are more and more cracks appearing" in the wall keeping out the far-right, said the political analyst Sophie Pornschlegel, of the Jacques Delors think tank.

"The EPP's argument is to say, 'We are not working with them – but we can't help it if they want to vote along with us.'"

'Stability of the EU'

Parliament insiders say there still exists an "institutional majority" bringing together the mainstream forces that had von der Leyen reelected.

But Pascal Canfin of the centrist Renew group believes she "does not feel bound" by it.

"If this ends up producing regular deals with the far-right, we will consider ourselves betrayed."

Nacho Sanchez Amor, the S&D coordinator on foreign affairs, urged the EPP to change tack, and instead "have a long view on what is going to be the stability of the Commission and European Union."

Meanwhile, the Patriots are rubbing their hands.

One group official pointed with satisfaction at the Venezuela vote, saying "we proved right away that there's an obvious new power balance."

"The EPP, centrists and Socialists won't have a lockdown on the parliament anymore," the official said, on condition of anonymity. "Things are going to be very different around here."