Slovakia's Constitutional Court will next week hear an appeal against a January verdict that cleared the current favourite to become the next Czech PM, Slovak-born entrepreneur-turned-politician Andrej Babis, of cooperation with the former Czechoslovak Communist secret police.

UPN, Slovakia's investigative institute of Communist-era oppression, is bringing the appeal against the Supreme Court ruling concerning billionaire Babis, who on September 6 had his immunity lifted by Czech MPs to allow the police to potentially charge him with fraud involving an EU subsidy.

Babis, head of the populist Czech ANO party, was a Communist party member and official at a Slovak state foreign trade firm during the 1980s. He has consistently denied having been an informant.

He was initially cleared by a lower court in June 2015. Two ex-agents of the StB, the secret police of the then Czechoslovakia, testified that he was never recruited. The fact that his name featured in the archives only indicated unwitting cooperation, they said.

In the 1990s, Babis, 63, moved to the Czech Republic. There he built up his Agrofert agro-chemicals and foodstuffs business and became the country’s second wealthiest individual before becoming finance minister and deputy PM after the 2013 election. He was dismissed from his position as finance minister earlier this year over unexplained business dealings.

UPN has insisted that files show Babis was an informer towards the end of the Communist era.