The Czech Republic’s likely next premier has become embroiled in another scandal after an audio tape was published on August 27 in which he allegedly described how he used the finance ministry to destroy a business enemy.

Andrej Babis, billionaire owner of the Agrofert agrochemicals group and leader of the populist Ano party, has refused to comment on the one-minute tape directly. However, he insisted that when he controlled the finance ministry the Financial Administration department was independent and it was perfectly legitimate for it to pursue a tax probe into the FAU Prerov company. “I suppose Financial Administration had a clear reason to secure some of the money," he told Czech media.

But the recording was immediately leapt on by Prime Minister Bohuslav Sobotka, whose Social Democrats rule in coalition with Ano, and by opposition politicians as more evidence of the businessman’s conflicts of interest and in particular his misuse of the ministry to benefit his companies.

Earlier this year the ruling Social Democrats and the opposition combined to pass a conflict of interests law, now before the Consitutional Court, that was dubbed the "Lex Babis" because it was clearly written to target Babis.

Rightwing opposition parties have also mounted a campaign againt the finance ministry’s tougher tax probes, which they argue have harmed small businesses and have sometimes been directed against Babis’ business rivals.

On the tape, a voice similar to Babis’s is heard saying “our people kneeled on FAU Prerov” and that “it is in bankruptcy, and its accounts and railcars have been frozen”.

FAU Prerov – which has a fuel depot at the site of Agrofert’s industrial chemicals wholesaler Precheza which Agrofert had allegedly previously tried to buy – was declared insolvent last year after the finance ministry’s tax office issued a seizure order. A court later found the order was illegal.

Agrofert has denied any interest in buying the fuel depot, which, following FAU Prerov’s insolvency, is likely to be put up for sale.

The prime minister, who sacked Babis over his alleged conflicts of interest in May, said on August 28 that the finance ministry must investigate the case within 30 days.

“I will also ask him to check whether the Treasury Department has interfered in any way, in violation of its competencies, with the tax administration," said Sobotka.

"I think the whole thing has to be scrutinised, it has to be checked and I expect the Treasury to provide all the necessary information within 30 days," he added.

However, a spokesman for Babis’ successor at the ministry, Ivan Pilny, who was nominated by the Ano leader, said the FAU Prerov case was now before the Supreme Administrative Court and therefore it would not intervene.

Petr Fiala, leader of the rightwing opposition ODS party, tweeted: “Babis’s ‘kneeling on’ sounds like the jargon of the underworld. At least before the elections we now know what his slogan ‘to run the state as a business’ means.”

The tape is just the latest published by Julius Shuman, an anonymous Twitter account under the name of Babis’ alleged secret police handler when he was an informer in the Communist period. Earlier this year Babis, a former Communist party insider who built up Agrofert with the help of mysterious backers, won a Slovak court judgement against the Slovak Memory Institution’s declaration that he was an informer.

The Julius Shuman Twitter account published a tape earlier this year in which Babis was heard discussing with a journalist on one of his newspapers when best to release a scandalous story about a Social Democrat minister. The recording confirmed suspicions that Babis was directing his media empire against his political rivals. Babis argues the recording was an entrapment.

The populist leader, who has made anti-corruption his party’s main promise, has been beset with financial scandals too, but he nevertheless remains well ahead in opinion polls before October’s general election. The most recent poll, by Median, gave his party a 12-point lead over the Social Democrats.

Babis has been accused of using a loophole to evade tax by making Agrofert issue tax-free CZK1 bonds and then buying the whole issue himself. The finance ministry is meant to be investigating the affair but critics argue that it is stalling until after the election. Babis says his use of the bonds was legitimate.

Parliament is poised to consider dropping Babis’ immunity over a police probe into an allegedly fraudulent application for EU aid for his Storks Nest resort. The EU’s anti-fraud watchdog OLAF is also investigating the case.

Babis, who denies any fraud, has attacked the timing of the police probe as politically motivated, saying that they should have waited until OLAF finished its investigation, something that it is only likely to happen after the election.