"This case does not impact me in any way," Avramopoulos told a press conference in Athens.
"It's a miserable case of slander with the contribution of false, hooded witnesses," he said, according to state news agency ANA.
Two former Greek prime ministers and eight former ministers, including Avramopoulos, have been named by protected witnesses -- whose identity is being withheld -- as allegedly involved in approving Novartis contracts and overcharging in return for kickbacks.
Greek anti-corruption prosecutors have asked parliament to hand over any files relating to the alleged bribery in light of the suspected involvement of the former ministers, who were in office between 2006 and 2015.
Avramopoulos, who was Greek health minister from 2006 to 2009, said Friday that the witness claims -- criticising his handling of a blood screening contract and a large order of avian flu vaccine -- were based on "rumour and hearsay."
"There is no evidence. It's lies," he said.
Greece's Justice Minister Stavros Kontonis last year said Novartis had likely bribed "thousands" of doctors and civil servants to promote its products.
He also accused Novartis of continuing to sell "overpriced" drugs even after the country was plunged into economic crisis in 2010 and huge cuts were imposed on state budgets, leaving many Greeks without access to affordable medicine.
Probes in the US, China
Novartis overcharges alone are estimated to have cost the Greek state some €3 billion ($3.7 billion).
Overall, similar practises across the health sector cost Greece some 23 billion euros between 2000 and 2015, investigators have said.
Novartis has issued a statement saying it was "aware of the media reports about our business practices" in Greece and that it was cooperating with the authorities.
Scores of people have been questioned in a probe ongoing since 2016, with anti-corruption prosecutors visiting Novartis's premises near Athens in early 2017 to gather evidence.
The case gained attention following a suicide attempt by a Novartis manager on New Year's Day last year in Athens.
That attempt was thwarted by police, and a judicial source said the manager was one of those questioned over alleged corruption.
The Swiss pharmaceutical giant was investigated by US authorities in 2014, accused of paying bribes in order to boost sales of some of its medicines, and was later fined $390 million by the US Justice Department.
In March 2017, Novartis also paid $25 million to settle claims involving its Chinese subsidiary.