British authorities have put on hold what they deemed a "disproportionate" European arrest warrant issued by Spain as it seeks to extradite Catalan separatist leader Clara Ponsati over her role in a failed independence bid, official documents have shown.

A Spanish interior ministry source told Reuters on Wednesday that British police would not put the warrant in their system because they judged it disproportionate, but no decision had been taken at the judicial level on rejecting the warrant.

In documents sent to the Interior Ministry and seen by Reuters, the British side said that "no further action will be taken by the UK at this time", but it allowed for the possibility of reopening the case at a later date if Spain can provide more information on the seriousness of the offence.

For now, the warrant was deemed "disproportionate under UK law", the documents showed.

Spain's Supreme Court on Tuesday reactivated a European arrest warrant for Ponsati, who currently lives in self-imposed exile in Scotland, and two other former Catalan leaders in Belgium for helping to organise a 2017 referendum deemed illegal by a Spanish court. The plebiscite set off a short-lived declaration of independence in Catalonia.

Ponsati is facing one charge of sedition, according to court documents issued in Spain, the same charge on which various independence leaders were sentenced in October to up to 13 years in prison.

Reacting to the British response, Catalan regional government head Quim Torra, a separatist, tweeted: "The international embarrassment of Spain and Spanish law is colossal".