ATHENS (Reuters) - Greece’s former prime minister Antonis Samaras filed a lawsuit against Alexis Tsipras on Thursday, accusing the current head of government of slander and “a villainous plot” against him over a bribery case.

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The case involves alleged bribery of Greek doctors, politicians and officials by staff of Swiss drugmaker Novartis. The company said this week it would take “fast and decisive action” if an investigation finds that its managers engaged in wrongdoing.

Greek prosecutors, who have been conducting an inquiry for more than a year and raided Novartis offices in Athens in early 2017, last week referred the case to parliament, which under Greek law is the only institution that can investigate ministers.

The house will soon decide whether to probe the roles of 10 socialist and conservative politicians mentioned in the file, including Samaras, former leader of the conservative New Democracy party, according to documents filed to parliament.

They have all strongly denied the allegations, calling the claims a fabrication and “a witchhunt” by Tsipras’ leftist-led government.

“Today, I filed a lawsuit against the prime minister. Because, under his responsibility, a villainous plot is being set up,” Samaras, who served as prime minister in 2012-2014, said in a televised statement. “The truth will shine.”

The office of Prime Minister Tsipras issued a statement saying: “the only one persecuting Samaras is his past.”

The lawsuit was also filed against other individuals, including prosecutors and witnesses under protection. They did not comment.

Tsipras’ Syriza party, which trails New Democracy in opinion polls, submitted an official request this week for a parliamentary committee to be formed to conduct an inquiry.

In charge since the height of Greece’s financial crisis in 2015, Tsipras has promised to crack down on corruption, which he often blames on his predecessors. Many Greeks blame the debt crisis which exploded in 2010 on political corruption.