Investigator Martin Bauer, who questioned Ecclestone for the case against the banker who accepted the alleged bribe, said Ecclestone was never able to give concrete details to back up his blackmail claim.
"It was all very vague," Bauer told the Munich state court, the dpa news agency reported. "Like a vanilla pudding that you can't nail to the wall."
Ecclestone, 83, is accused of making the payment to banker Gerhard Gribkowsky, who is serving an 8 1/2-year sentence for taking the money. He is charged with bribery and incitement to breach of trust, and could face up to 10 years in prison if convicted.
Prosecutors allege the payment was meant to facilitate the sale of Munich-based bank Bayern LB's stake in F1 to a buyer of Ecclestone's liking. Gribkowsky was in charge of selling that 47 per cent stake in F1 in 2005.
When his trial opened last week, Ecclestone told judges in a statement read by his attorneys that he gave the banker the money because he was "blackmailed" and worried Gribkowsky would falsely accuse of him of being in charge of a trust fund set up for Ecclestone's former wife and their children — possibly incurring a huge British tax bill.
Gribkowsky is due to testify during the trial's next session, scheduled for May 9.
Ecclestone's current wife, Fabiana Flosi, was in court, sitting alone in the public seats. She joined Ecclestone and his attorneys in the courthouse cafeteria for lunch.