EFA MEPs Diana Riba and Jordi Solé have spoken out against attempts to politicise the operation of the European Arrest Warrant.
The European Parliament has been reviewing the implementation of the European Arrest Warrant, which allows those accused of serious crimes to be extradited from one EU country to another.
But the issue has now been seized upon by Spanish nationalists who propose including 'crimes against the constitutional order' amongst the list of offences eligible for extradition.
The MEPs warned of the risk of opening the doors to arbitrary detentions in states with little regard for justice and freedom.
Speaking in the debate, EFA MEP Diana Riba said:
"The European Arrest warrant is a mechanism that operates under the principles of mutual trust between states and respect for fundamental rights.
"But mutual trust cannot be confused with blind trust, since there are still European countries with obvious deficiencies in judicial matters. That is why the debate should focus on how to strengthen procedural safeguards, and not on how to get a speedy arrest.
"This parliament cannot open debates or propose reforms of mechanisms just to satisfy the repressive impulses of some. We risk the credibility of this Parliament.
"Adding the crime of constitutional integrity to the list of direct extradition crimes will not facilitate the arrest of Catalan leaders, but will open the doors to unjust or arbitrary extraditions for those States with little regard for the European values of justice and freedom."
EFA President Jordi Solé said:
"Once again we see Spanish MEPs from the socialists to the far-right taking advantage of issues at European level to exploit for domestic political reasons.
"That's certainly the case with the current debate around the European arrest warrant, an important tool to deal with criminality in the EU.
"It is unfortunate that certain Spanish politicians are seeking to exploit this not in the interests of justice in Europe, but simply for internal political point scoring.
"The European arrest warrant is there to facilitate the detention of those accused of serious crimes, not as a tool to imprison or intimidate political opponents.
"Including an offence related to constitutional integrity would pose grave danger to freedom of expression and of course the right to self-determination."