Mlada Fronta Dnes, a Czech daily, appears to have documented quite well that Josef Tosovsky colloborated with the state police in the final years of Communism in the late 80s. Tosovsky was the Czech Prime Minister in 1997-8 as part of a caretaker government and was also governor of the Czech National Bank during some very difficult times. Rather than admitting to the extent of his involvement, Tosovsky has issued a denial. Fleet Sheet (see below) bills this an implausible denial and suggests that it makes matters worse and raises further questions.
Another Czech newspaper Hospodarske noviny goes one further in its editorial suggesting that Tosovsky was blackmailable for all his years of power. It's worth pointing out that the banking industry lost 100s of billions of crowns during his time in charge. The banking system practically collapsed and became almost fully foreign-owned, but that's a story for another time.
Hat tip to Fleet Sheet, a daily English-language news bulletin devoted to the business and political activities in the Czech Republic.