Mr Assange, who is currently holed up in London’s Ecuadorian embassy, has shared multiple videos of protests in Barcelona along with messages of support to the people of Catalonia.
But Spanish officials have claimed he is spreading messages “contrary to reality” and are believed to have put pressure on Ecuadorian representatives to silence the outspoken hacktivist – claiming his comments are breaching his asylum status.
On the eve of the Catalonia referendum, Ecuadorian President Lenin Moreno said: “We have asked him in a cordial way to stop commenting on Ecuador’s policy or on other countries’ policies because his asylum status does not allow him to do so.
“He is surpassing that condition.”
Mr Assange has become a vocal supporter of Catalonian secession amid furious protests and scenes of police brutality in Barcelona and beyond.
Spain has long maintained the referendum was illegal, and have clamped down on its instigators along with issuing a European arrest warrant for former Catalan president Carles Puigdemont.
Diplomatic sources claimed the last time Spain contacted the Ecuadorian authorities was after a meeting between Assange and the editor Oriol Soler – who aided Mr Puigdemont in his push for independence.
Spanish authorities also believe Mr Assange helped keep open referendum websites the Government was closing down following the orders of the Constitutional Court.
In addition to the meeting with Oriol Soler, there is the offer of 20,000 euros for whoever reveals police intervention plans for October 1, as well as their costs.
The Spanish authorities have since reportedly told Ecuadorian counterparts Mr Assange is spreading messages “contrary to reality” – adding his statements place pressure on Madrid to explain the situation due to swaying public opinion.
Express.co.uk has contacted Mr Assange for comment.
The allegations come as Spain blames Russian-based groups for attempting to manipulate social media by promoting Catalonia’s independence as a way of trying to destabilise Madrid.
Spain’s defence and foreign ministers said they had evidence that state and private-sector Russian groups, as well as groups in Venezuela, used Twitter, Facebook and other websites to publicise the separatist cause and swing public opinion behind Catalonia in the run-up to the controversial October 1 referendum.
The referendum has plunged Spain into its worst constitutional crisis in decades and now officials are accusing Moscow of meddling before the vote.
Spanish Defence Minister Maria Dolores de Cospedal said: “What we know today is that much of this came from Russian territory.
“These are groups that, public and private, are trying to influence the situation and create instability in Europe,” she told reporters at a meeting of European Union foreign and defence ministers in Brussels today.
Additional reporting by Maria Ortega