Calling on Brussels to do "much more"to promote multilingualism, which they described as EU citizens' "democratic right", MEPs from the European Free Alliance (EFA) also demanded more EU action to save endangered languages like Corsican, Breton, Scots and Occitan.
"Catalan, Basque, Galician, Gaelic and Welsh among them total approximately fourteen million speakers yet continue to be denied official status at EU level," said the EFA members, who represent stateless nations, regions and minorities in Europe.
The conference, which saw simultaneous interpretation into Catalan and Welsh provided on European Parliament premises for the first time, gathered policymakers and academics from across the continent.
Spanish politics has long been fraught by difficult relations between Madrid, which currently holds the EU's six-month rotating presidency and the regions. Separatist movements exist in Catalonia, the Basque Country and Galicia, where the Catalan, Basque and Galician languages are spoken.
Insisting that his government is committed to multilingualism, which he described as part of the EU's DNA, Pau Solanilla, executive advisor to the Spanish Secretary of State for EU Affairs, nevertheless warned that there is political resistance to minority languages in some member states.
Describing identity as a "thorny issue" to which politicians can be "allergic", Solanilla said "some politicians fear separatist movements" could rise up as a result of linguistic diversity.
"Linking identity to linguistic diversity can cause problems," warned Solanilla. Nevertheless, he said the Spanish government was "now ready" to co-operate on language issues and expressed hope that Spain's "co-official" languages, Catalan and Basque, would be regularly used in the European Parliament soon.
There are precedents for minority language use in the EU institutions. Last July, an agreement struck between the European Commission and the UK government paved the way for the Welsh to be able to write to the EU executive in their native language (EurActiv 09/07/09).
Moreover, in November 2008, Welsh was heard and interpreted at EU level for the first time during a meeting of culture ministers (EurActiv 24/11/08). Since then, the Welsh have been able to write to the European Council, and receive a written response, in their native tongue.
But EFA members believe these efforts are far from enough and want the EU institutions to use changes introduced by the Lisbon Treaty to protect the rights of linguistic minorities (EurActiv 01/12/09).
Catalan 'invisible at EU level'
Last week's hearing, meanwhile, heard a passionate plea for Catalan, which is spoken by around 10m people in four countries and is the official language of Andorra, to become an official EU language.
"Catalan is used by millions of people every day but it is still invisible at EU level," lamented Kolja Bienert of the organisation Horitzo.eu, which promotes the interests of Catalonia in the EU.
Regarding its use in the EU institutions, Bienert complained that Catalans must rely on the political goodwill of the Spanish government to make their language heard.
"It's easy to make a language official. A government just has to ask for it, as the Irish case proved," he said, adding: "The European Parliament shows a lot of goodwill but there is no legal enforcement, and it does not sign agreements with national governments."
Echoing Bienert, Joan Bernat, a former MEP and specialist in sociolinguists, said governments hold the key to whether a language is granted official status at EU level, not number of speakers or history.
"Number of speakers is not at all a condition. Look at Maltese or Estonian. It's not history either. We have Greek today, but not Occitan, the most important language of the Middle Ages. What matters is the language of the state. If the state applies official status to a language, it can be an official EU language too," Bernat said.
English 'a reality we can't ignore'
A representative of the European Commission responded by saying that it was up to member states to propose to the EU executive that a language become official, as was the case with the Irish government.
Speaking in a personal capacity, he said "languages are boundless and there are no frontiers. We don't want to confine languages to borders. We want them to spread naturally. A language is not the property of a state".
The Commission official concluded, however, by sounding a cautious note. "We need to be realistic, and English is a reality that we can't ignore. We have to be able to communicate with one another."
The EU executive, which recently merged the multilingualism portfolio with the education, culture and youth dossiers, is next due to review its languages policy in 2012.