A Polish newsmagazine said Sunday it had obtained a covert recording of a former minister declaring that the ruling party had settled the debts of a rival candidate in the 2005 presidential election in exchange for his withdrawal from the race.

The report in Wprost magazine was the latest to emerge from mysterious tapes that have tarnished the government's reputation and confronted Prime Minister Donald Tusk with his biggest challenge since taking power in 2007.

Wprost published what it said were excerpts of a secret conversation at a restaurant between former Infrastructure Minister Slawomir Nowak and Dariusz Zawadka, a former head of military special forces.

The transcript alleges that the two men discussed the 2005 presidential election, in which prominent heart surgeon Zbigniew Religa announced he would run but later withdrew and backed Tusk. "In 2005, I remember, we took over his debts so that he pulled out," Nowak was quoted by Wprost as saying.

Tusk lost the election to Lech Kaczynski, who died in a plane crash in 2010. Tusk became prime minister in 2007.