The witness had advised car manufacturers like Ferrari and Daimler at about the same time as Ecclestone paid Gerhard Gribkowsky the alleged $44 million bribe.
Ecclestone argues Gribkowsky was effectively extorting him, but the prosecutors say the 83-year-old was in a mood of desperately clinging to power.
Wednesday's witness did not seem to help the diminutive Briton's case.
The witness said key manufacturers involved in F1 were seriously threatening to split from the series and set up their own motor racing category.
Some, the witness testified, saw Ecclestone as a "key" to the success of a premier motor racing series, and had no intention of proceeding without him.
Others were apparently less bothered, or even happy with the thought of Ecclestone no longer being involved, which could have meant the freeing up of more commercial income.
According to APA, as the translator relayed the testimony to Ecclestone in English, the F1 supremo "shook his head several times, puffed out his cheeks and made notes".