Junqueras is one of three pro-independence Catalan MEPs who have so far been unable to take up their seats after the EU elections in May.
The other two are Carles Puigdemont and Toni Comín, neither of whom are members of the Greens/EFA group in Parliament.
Speaking at a news conference in Strasbourg, German deputy Keller said Junqueras should not be disbarred any longer, saying, “He was democratically elected, he has a right to be in Parliament and should be allowed to take up his seat here.”
Catalan separatist leaders Puigdemont, Comín and Junqueras have not been able to take their seats in Strasbourg as the Spanish electoral authority has not recognised them as members.
Puigdemont and Comin have lived in self-imposed exile since warrants were issued for their arrest in Spain after a failed bid for secession for Catalonia in 2017.
Instead of traveling to Spain to pledge allegiance to the Spanish constitution in person, as is required to take seats in the Strasbourg assembly, both sent in written statements of allegiance, which were not accepted.
Junqueras, currently imprisoned in Spain, was not allowed to leave jail to take the pledge and, along with Puigdemont and Comín, was left off Spain’s list of members, which numbered 51 rather than 54.
“He was democratically elected, he has a right to be in Parliament and should be allowed to take up his seat here” Ska Keller MEP
Hundreds gathered outside the Parliament in Strasbourg this week, many waving pro-independence Catalan flags, to protest against the exclusion of the three Catalan separatist leaders.
The EU General Court in Luxembourg on Monday dismissed an application by Puigdemont and Comín to take their seats at the start of the session while challenges to decisions by the Spanish authorities and the Parliament to bar them are considered.
Keller, speaking earlier this week at a news briefing in Parliament, told reporters, “Any future Parliament President would certainly have to also look into this, because it’s also a matter of how do you defend the rights of those who have been elected into the European Parliament.”
Meanwhile, Catalan Foreign Affairs Minister Alfred Bosch points out that the three Catalan MEPs were "chosen by two million European citizens" who should be represented in a "fully democratic" European Parliament.
The assembly’s constitutive session this week shows that the Catalan issue “is not a Spanish internal affair” but a European one, he said.
He regretted that "the bureaucratic obstacles that a Member State, in this case, the kingdom of Spain", puts [in the way] weigh more than "the votes of citizens" in the European Parliament.
Bosch said, “In the hemicycle there are three missing MEPs who have been chosen by two million European citizens".
“In the [Parliament] hemicycle there are three missing MEPs who have been chosen by two million European citizens" Alfred Bosch, Catalan Foreign Affairs Minister
This was, he said, "a violation of the most basic democratic rights" of the Catalan voters, adding, "We will not stop demanding that those who have been elected can be here representing European citizens".
In a speech this week in Strasbourg, Bosch reaffirmed the “pro-European nature” of Catalonia and said that the Catalan political situation "is not a Spanish internal affair but a matter that goes straight to the heart of what the European project is".
"The votes of the citizens of Europe must prevail", he said.
Bosch said that the three MEPs “need to be able to act as MEPs in the European Parliament” and noted that Junqueras was also a candidate for the presidency of the European Commission.
He said, "He is in jail and they have not let him go to be here or to get the accreditation. He can’t even be here when there is a group of European political parties that defend him as a Spitzenkandidat".
The three elected MEPs "have their political rights intact since they have not been convicted. If they could stand for election, they should now be able to be here and enter the European Parliament to represent their voters,” Bosch added.