Prosecutors were required to notify parliament of the investigation in order to have Kohl's immunity from prosecution lifted. If immunity is lifted, the preliminary probe would seek to determine whether Kohl should face criminal charges.
Parliament's announcement represented a new peak in a scandal that exploded with Kohl's first admission a month ago that he controlled secret party accounts while running his conservative party with an iron grip for a quarter-century.
Parliament's president, Wolfgang Thierse, received a letter Wednesday from prosecutors saying they "intend to open a preliminary investigation against the member of parliament, Dr. Helmut Kohl," the statement said.
Thierse must now consult with party leaders to decide whether to block the probe. If party leaders take no action within 48 hours, the probe may proceed. However, if there is disagreement among the parties, a decision could be delayed by weeks.
Kohl's office refused to comment on the development.
Kohl has admitted receiving up to $1 million in cash contributions as leader of Germany's Christian Democratic Union during 1993-98. He has vowed to keep his word and not name the secret donors, even though anonymous party contributions are illegal in Germany.
The donations were kept off the books and could lead to heavy fines for the party, prompting speculation that Kohl would be investigated for possible charges of breach of trust.
Prosecutors in Bonn, which was the seat of federal government when Kohl was in power, were expected to issue a statement later Wednesday.
Beyond admitting in interviews that he made a mistake, the man who governed Germany for 16 years has remained largely unrepentant. But the scandal is clouding the 69-year-old former leader's place in history as the chancellor who united Germany after the fall of the Berlin Wall.
Prompted by one of the covert donations to the party, parliament launched its own inquiry earlier this month to examine whether decisions in Kohl's government were influenced by payoffs, something Kohl has repeatedly denied.
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