PRAGUE (AP) — Former Czech populist Prime Minister Andrej Babis lost his final appeal in Slovakia Wednesday in a case concerning allegations that he collaborated with communist-era secret police in what was then Czechoslovakia.

Babis, who was born in Slovakia, was suing the Institute for National Memory, which holds parts of his secret police files following the division of Czechoslovakia into the Czech Republic and Slovakia in 1993.

In a decision on Feb. 1 but only published Wednesday, Slovakia’s Constitutional Court, the highest court in the land, upheld the rulings by lower courts dismissing the case.

Some of the files were destroyed, but the institute said those that still exist contain evidence that Babis was an agent under the code name “Bures” from 1982. Babis has vehemently denied that.

The regional court in the capital, Bratislava, originally rejected the lawsuit in 2018, but the Constitutional Court ordered a retrial, saying the institute could not be sued and the respondent should be the Slovak Interior Ministry.

The regional court dismissed the case again in 2022, followed by a similar ruling from the Supreme Court in September last year.

Babis challenged that with a complaint filed with the Constitutional Court whose verdict completed the case.

Babis, a billionaire, is currently in opposition after his populist ANO centrist movement lost the 2021 parliamentary election. He was running to become the Czech president in the election for the largely ceremonial post in January last year but lost to Petr Pavel, a retired army general.