European leaders have managed a united front in backing Spain against Catalan separatists, but the issue shows up deep divisions in the fourth biggest group in the European Parliament — the Liberals.

The Alliance of Liberals and Democrats for Europe (ALDE) is at times less an alliance than a fractious assembly with disparate credos and little to unite them. Its membership ranges from Spain's centrist Ciudadanos to the political vehicle of a sometime Euroskeptical Czech billionaire and ethnic Turkish Bulgarian parliamentarians.

In recent weeks, the Catalan debate has deteriorated into a shouting match between Liberal MEPs and crystallized the challenge facing former Belgian Prime Minister Guy Verhofstadt, who presides over ALDE. He's the one who has to herd these cats, and it looks like an increasingly trying exercise.

The disputed Catalan independence vote — and Madrid's response to it — has sparked a bitter spat that manifests itself in loud arguments at internal meetings, snide emails and rumors of defections.

The current acrimony centers on Ramon Tremosa i Balcells, the one MEP in the group who backs independence for Catalonia.

He has been regularly lambasted by fellow ALDE MEP Enrique Calvet Chambon in internal emails seen by POLITICO for alleged disloyalty to the group after he sat with Flemish nationalist MEPs during a debate on Catalonia in Strasbourg.

"As you all know, our colleague Tremosa joined another Group during the plenary; he abandoned his seat to occupy another seat in the area of the ECR Group," said Calvet Chambon in one email. He has subsequently called for Tremosa's party to be banned in Spain ahead of December regional elections.

"They're constantly bringing their internal issues to our group meetings" — Kaja Kallas, Estonian ALDE member

A few days before, during an internal ALDE meeting, Calvet Chambon screamed insults at Tremosa before storming out of the room, according to people present at the meeting, while the Czech Group Vice President Pavel Telička compared the tactics used by Spanish police in Barcelona to Russian actions in the Cold War.

"They're constantly bringing their internal issues to our group meetings," complained Kaja Kallas, an ALDE member from Estonia, adding that warring MEPs refused to sit in the same room at one point.

Verhofstadt has sided with the seven pro-union Spanish MEPs in the group, publicly mocking the deposed Catalan President Carles Puigdemont as a bungling version of the Belgian cartoon character Tintin.

"I'm happy [Tremosa's] isolated," said Javier Nart, an MEP from the unionist Spanish party Ciudadanos, describing the Catalan MEP as "a sectarian nationalist."

Guy's choice

ALDE was pushed into fourth position behind the Euroskeptic European Conservatives and Reformists (ECR) after the 2014 election, when support for liberal parties in the U.K. and Germany collapsed. It currently has 68 MEPs. The size of the group dictates what funding it gets, which committee chairmanships it secures and how much speaking time it is allocated in plenary debates.

Verhofstadt's job of keeping the unruly group together has also been complicated by last month's election victory in the Czech Republic for the populist billionaire Andrej Babiš. His party, ANO 2011, is in the ALDE fold and Babiš is set to become the country's prime minister after running a campaign that appealed to voters' hostility to joining the eurozone — something Verhofstadt regards as sacrosanct.

Even so, the ALDE leader put on a brave face after meeting Babiš, saying he thought he could "count on ANO to push for such a reform agenda."

Less optimistic were MEPs within his own political group. "At a certain point ALDE and ANO will have to sit down and ask 'Do we still match?'" said MEP Telička, a former European commissioner who quit ANO before the election over Babiš' stance on the eurozone.

What's clear is that Verhofstadt's support for a genuinely federal EU — earlier this year he called for the EU to be made a "real union and not a loose confederation of nation states" — is not shared by all 67 of his fellow ALDE MEPs. "You don't always have to agree with Guy on every issue," said Telička.

Verhofstadt's challenge is to bridge the ideological divide; his reaction to Babiš' victory is instructive of his approach. In a statement to POLITICO, Verhofstadt rejected suggestions Babiš was a Euroskeptic, saying he "is critical of how the current European Union works, but has constructive proposals to make it better."

The desire to protect its numbers can sometimes lead to contradictions in ALDE's professed pro-EU stance.

Another question mark hovers above ALDE's four Bulgarian MEPs who belong to the country's Turkish minority party, the Movement for Rights and Freedoms (MRF), which was founded in 1990 by Ahmed Dogan, named in a 2007 official report as a paid agent of the country's communist-era secret police.

The appointment of controversial businessman Delyan Peevski, one of the party's biggest names, as head of Bulgaria's security agency in 2013 almost brought down the government after protests kicked off. A year later, he won a seat in the 2014 European Parliament election near the top of the MRF list, although he subsequently decided to give it up.

French menace

Recent poachings from ALDE by rival groups include Portugal's José Inácio Faria, who defected to the center-right European People's Party, and Brian Crowley of Ireland's Fianna Fáil, who moved to the ECR after the 2014 election.

But the desire to protect its numbers can sometimes lead to contradictions in ALDE's professed pro-EU stance.

Seeing a chance to shunt the ECR back into fourth position at the start of this year, Verhofstadt courted the 17-strong group of MEPs representing Italy's populist 5Star Movement. He was forced to back down after the majority of his members revolted, citing the 5Stars' hostility to the euro as a red line.

Verhofstadt might have hoped that his political gang would have benefited from the rise of France's Emmanuel Macron. The French president's centrist, pro-European message should, on the face of it, have made him a natural political bedfellow.

But Macron has so far declined to align his La République en Marche with ALDE. With the 2019 European election on the horizon, that leaves Verhofstadt trying to keep the peace among his troops while fending off advances from other political groups on the lookout for new recruits.

The threat from Macron — who has indicated his desire to create a pan European centrist party and even poached ALDE MEP Sylvie Goulard to be his defense minister — is likely greater for ALDE than any other political group. Since his election, Macron has flirted with Ciudadanos, Belgian Prime Minister Charles Michel and Luxembourg's Xavier Bettel — parties with 10 MEPs that currently belong to ALDE.

With such loose ties holding them together, ALDE's members could be easy picking for a new Macron-inspired movement in the European Parliament. Despite his efforts to create a broad ideological church, that could leave Verhofstadt without much of a party to lead into the EU parliamentary election in 2019.