After an overnight debate, a broad majority from all parties voted in favour of setting up a preliminary commission of inquiry into the issue, a move also requested by the 10 politicians themselves in order to clear their names.
“Is there anybody who doubts this company's opaque practises?” Prime Minister Alexis Tsipras told parliament, arguing that thousands of doctors were illegally paid to prescribe Novartis drugs, that the Swiss giant helped “manipulate” the prices of its products and laundered money through medical congresses of “questionable merit.
Only parliament has the power to investigate former ministers for actions taken while in power.
Among the 10 senior politicians allegedly named by protected witnesses in a mostly US-based investigation are conservative ex-PM Antonis Samaras, EU migration commissioner Dimitris Avramopoulos and central banker Yannis Stournaras.
They all deny wrongdoing.
“I know Tsipras detests me, but you have gone too far. You will be held to account for this frame-up against me,” Samaras told parliament, accusing the government of engaging in a “mud-slinging war”.
The parliamentary commission has a month to recommend prosecution of any confirmed suspects to the chamber.
The Swiss giant is suspected of having bribed decision-makers and doctors between 2006 and 2015 to build a commanding position in the Greek health market, as well as secure inflated prices for its products even though cheaper alternatives were available.
Tsipras has pledged to employ “every power afforded by national and international law” to recover billions of euros believed to have been lost to the Greek health system as a result of the scheme.
But his opponents say the government is trying to deflect attention from the economy and foreign policy issues.
Critics also note that the allegations — some based on second-hand accounts – are not accompanied by hard evidence and include glaring factual errors.
“In a case file of 2,500 pages there are just two paragraphs mentioning my name… and every single word is untrue,” the EU migration chief said in his lawsuit.
The alleged testimony, leaked to the press, faults Avramopoulos' handling of a blood screening contract and a large order of avian flu vaccine.
Greek central banker Yannis Stournaras, a former finance minister under Samaras, is among those cited in the case file.
Stournaras, also named because his wife's PR company organised congresses sponsored by Novartis, dismissed the claims as “idiotic” and “foul slander.”
The allegations also target the socialist party's parliamentary spokesman, Andreas Loverdos, and the deputy chairman of the main opposition conservative party, Adonis Georgiadis.
Novartis' overcharging alone is estimated to have cost the Greek state some €3 billion ($3.7 billion).
Overall, corruption across the health sector cost Greece some €23 billion between 2000 and 2015, investigators have said.
Greece's Justice Minister Stavros Kontonis last year said Novartis had likely bribed “thousands” of doctors and civil servants.
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.
The OECD has estimated that drugs purchases in Greece jumped from 23.6 percent of total health spending in 2006 to 30.7 percent in 2011. They fell to 25.9 percent in 2015 under pressure from international creditors.
Novartis has said it has been cooperating with US and Greek authorities for over 14 months, whilst conducting an internal audit of its own.
The Swiss giant has already paid multi-million dollar fines in the United States, China and South Korea to settle corruption cases.