Junior partner’s decision to withdraw from government may trigger early polls.
The investigation into alleged wrongdoing at the ministry resulted in the sacking last month of Andrzej Lepper, the former agriculture minister, who also heads one of the junior partners in the coalition government.
The scandal involves the suspected payment of bribes to redesignate agricultural land for commercial use.
The prime minister and his twin brother, Lech Kaczynski, the country’s president, have said that they believe early elections could be a way out of the crisis, but so far have stopped short of calling for them.
The next regular elections are set for 2009.