The journalist Costas Vaxevanis was arrested on Monday following a legal suit lodged against him by former conservative prime minister Antonis Samaras for defamation.
Vaxevanis had been at the Athens appeals court for the hearing of another legal suit against him brought by Lina Nikolopoulou, the wife of Bank of Greece Governor Yannis Stournaras.
The journalist was exonerated in that case and then immediately arrested in connection with the new suit.
On Sunday, Samaras sued Vaxevanis over a Facebook post last week in which he accuses the ex-conservative leader of lying about his involvement in the Novartis case.
Samaras is among 10 high-profile politicians named by prosecutors in an investigation into alleged bribes paid by the Swiss pharmaceutical giant Novartis to secure preferential treatment in Greece.
“A defendant has the right to defend himself even by lying. In this regard, Antonis Samaras is justified in lying in order to get out of a difficult spot,” Vaxevanis, who is the publisher of the newspaper Documento, wrote.
A close associate of Samaras described the post as “vulgar and provocatively insulting.” He also accused Vaxevanis of acting on “orders.”