BRATISLAVA(Reuters) - Slovakia’s top court on Thursday overturned rulings by lower courts that had cleared the frontrunner to become Czech prime minister of cooperation with communist-era secret police (StB), a court spokeswoman said.

The leader of ANO party Andrej Babis signs his books during an election campaign rally in Prague, Czech Republic September 28, 2017. Picture taken September 28, 2017. REUTERS/David W Cerny

Andrej Babis, who is almost certain to win a parliamentary mandate in the Oct 20-21 vote, has admitted to meetings with StB officers in the former Czechoslovakia, but insists he only discussed the country’s economic interests.

Especially for older Czechs and Slovaks, the injustices of the communist era of their joint past are still raw nearly 30 years on and any suggestion of collusion could still be a stain on his reputation.

If he were to be listed as an informer, it would not bar Babis, 63, from elected office and he questioned the timing of the decision by Slovakia’s Constitutional Court.

“I never signed collaboration with the StB and never collaborated with the StB ...,” Babis said via a spokeswoman.

“Of course I am bothered that this issue is returning to the beginning after five years and will be abused in a political fight ...a few days ahead of an election.”

Babis said he would fight the ruling with another lawsuit, if needed, having launched the original lawsuit to clear his name.

The decision returns to lower court the lengthy battle over Babis’ activities in the 1980s, when he was a member of the Czechoslovak ruling Communist party and worked for a state foreign trade company.

Babis moved from Slovakia to the Czech Republic in 1993 after the dissolution of Czechoslovakia. He then built up his Agrofert chemicals business and joined politics in 2011.

StB files released by Slovakia’s investigative institute of communist-era oppression, UPN, say Babis was an informer of the secret police.

Several Slovak courts including the Supreme Court have cleared Babis of the allegations.

Those rulings were based on evidence given by former StB agents, who testified that Babis was never recruited and his appearance in the archives, under a code name, only meant unwitting cooperation.

“The reasoning by the Constitutional Court was that UPN can not be sued in this case because it did not author the StB documents. The court also said former StB agents are untrustworthy witnesses by definition,” UPN attorney Pavol Polacek from the Polacek&Partners law firm told Reuters.

“Legal opinion of the Constitutional Court is binding for lower courts so the regional court will have to dismiss Babis’ lawsuit,” he added.

Babis is also facing fraud charges in the Czech Republic in a case involving a 2 million euro EU subsidy a decade ago. He has repeatedly denied any wrongdoing.