The Greek parliament has voted to investigate 10 prominent politicians, including two ex-prime ministers, over allegations they allowed bribery by the Swiss pharmaceuticals company Novartis.

Under Greek law, only parliament can investigate its own members and lift their immunity.

The vote followed a 20-hour debate, in which PM Alexis Tsipras said: “We won’t help cover up… one of the biggest scandals in modern Greek history”.

The 10 politicians deny wrongdoing.

They have condemned what they called a political “witch-hunt”.

They are alleged to have let Novartis bribe doctors so they would prescribe its drugs at inflated prices.

Prosecutors believe the alleged price-fixing could have cost the state €3bn (£2.7bn; $3.7bn) during a financial crisis that imposed hardship on many families.

Some politicians are also suspected of accepting bribes and there are allegations of money-laundering.

They held office from 2006-2015. Novartis says it is co-operating with the investigation.

The Swiss medicines giant told the BBC it had not received any formal allegations or indictments from the authorities investigating the case, and that media coverage “included many sensational and unfounded claims, in a politicised debate of which Novartis should not be a part”.

But it said it would “take fast and decisive action and do everything possible to prevent future misconduct” if any wrongdoing was found.

It said: “While Novartis continues to co-operate fully with the Greek and US authorities, we have also been conducting our own comprehensive internal investigation.

“We are determined to fully understand the situation and accept responsibility for any actions that fell below our high standards of ethical business conduct.”

A Greek parliamentary committee will assume the role of an investigating judge.

Prosecutors referred the case to parliament this month, after spending more than a year investigating.

The EU rescue of Greece during its debt crisis involved big cuts in healthcare spending and other public services.

The leftist Syriza-led government is wrestling with a crisis that erupted under previous conservative New Democracy and socialist Pasok governments.

Those named in the allegations include ex-finance minister Evangelos Venizelos, current central bank governor Yannis Stournaras and ex-health minister Dimitris Avramopoulos, who is now EU migration commissioner.