Authorities at GCHQ, the government eavesdropping agency, are facing embarrassing revelations about internal correspondence in which Wikileaks founder Julian Assange is discussed, apparently including speculation that he is being framed by Swedish authorities seeking his extradition on rape allegations.

The records were revealed by Assange himself in a Sunday night interview with Spanish television programme Salvados in which he explained that an official request for information gave him access to instant messages that remained unclassified by GCHQ.

A message from September 2012, read out by Assange, apparently says: "They are trying to arrest him on suspicion of XYZ … It is definitely a fit-up… Their timings are too convenient right after Cablegate."

The messages appear to contain speculation and chatter between GCHQ employees, but Assange gave little further explanation about exactly who they came from.

The WikiLeaks founder, who has spent the past 11 months in the Ecuadorian embassy in London to avoid arrest and extradition to Sweden, claimed GCHQ had been unaware that it might have anything on him that was not classified.

"It won't hand over any of the classified information," he said. "But, much to its surprise, it has some unclassified information on us."

"We have just received this. It is not public yet," he added.

A second instant message conversation from August last year between two unknown people saw them call Assange a fool for thinking Sweden would drop its attempt to extradite him.

The conversation, as read out by Assange, goes: "He reckons he will stay in the Ecuadorian embassy for six to 12 months when the charges against him will be dropped, but that is not really how it works now is it? He's a fool… Yeah … A highly optimistic fool."

"This is what the spies are discussing amongst themselves," Assange told the Spanish television presenter Jordi Evolé.

The Cheltenham-based agency said: "We can confirm that GCHQ responded formally to the subject who made the request. The disclosed material includes personal comments between some members of staff and do not reflect GCHQ's policies or views in any way.

GCHQ is exempt from the Freedom of Information Act. However, it is understood that Assange's request was a subject access request, a mechanism under the Data Protection Act that can be used by individuals to obtain personal information that bodies hold about them.

On its website, the agency says : "As one of the UK's intelligence and security agencies, we gather and analyse digital and electronic signals from many channels, from all corners of the world".

"Converting this information into intelligence material, we play a significant role in informing national security, military operations, police activity and foreign policy."