The Greek prime minister, Alexis Tsipras, has called for parliament to investigate whether two of his predecessors and eight former ministers accepted bribes from the Swiss drugmaker Novartis, after allegations of industrial-scale bribery involving senior politicians.

The former PMs Antonis Samaras and Panagiotis Pikrammenos, the governor of the Bank of Greece and the EU’s migration commissioner were all identified as alleged beneficiaries of bribes in a report compiled by anti-corruption prosecutors with the help of US authorities.

Novartis is alleged to have bribed politicians to approve overpriced contracts and to have made payments to thousands of doctors as part of concerted efforts to boost sales between 2006 to 2015.

The claims have rocked Greek society since coming to light last week. One serving government minister claimed the kickbacks surpassed €50m and resulted in costs of more than €4bn to the Greek public health system.

The deputy justice minister, Dimitris Papangelopoulos, said it was “the biggest scandal since the establishment of the Greek state” almost 200 years ago.

Widening the net on Monday, Tsipras said it was imperative there could be no cover-up. “We will make use of every power afforded by national and international law to recover the money stolen from the Greek people down to the last euro,” the leftist leader told MPs in his Syriza party. “We will do everything we can to reveal the truth.”

MPs will vote on establishing a committee of inquiry later this month. Only parliament has the power to investigate politicians for alleged infractions during their term in office.

The allegations have been rebutted vehemently by the accused. The report’s reliance on three unnamed witnesses – who are currently under government protection – has been especially criticised, and legal experts contend that the claims would not stand up in court.

The EU commissioner Dimitris Avramopoulos demanded that the identity of the witnesses be revealed and expressed his “disgust” at what he said were fabrications created by “sick minds”. He stands accused of purchasing 16m anti-flu vaccines from Novartis while health minister between 2006 and 2009.

Echoing opposition claims that the charges are politically motivated, Samaras, who has been accused of accepting suitcases stuffed with cash while he was PM, said it was “the most ruthless and ridiculous conspiracy theory ever”. He pledged to take legal action against Tsipras.

Pikrammenos, who formerly presided over Greece’s highest legal body and headed a caretaker government in May-June 2012, said he had never known anyone at Novartis. Evangelos Venizelos, a former deputy premier and finance minister also named in the report, denounced the claims as “a cheap political diversion”.

Tsipras’ two-party coalition government has long been lagging in opinion polls, the price of applying stringent austerity measures in return for the debt-ridden country receiving rescue funds from the EU.

In a statement on Monday, Novartis said it was cooperating fully with Greek and US authorities. “We have also been conducting our own internal investigation,” the Basel-based company said. “We are determined to fully understand the situation and accept responsibility for any actions that fell below our high standards of ethical business conduct. If any wrongdoing is found we will take fast and decisive action and do everything possible to prevent further misconduct.”

Novartis has faced similar investigations in recent years. Last year South Korea fined the company $48m for offering kickbacks to doctors.