[EU Politic] which "European party" has done the most to prevent a new Qatargate ?

In the context of the European election next month. I am surprised that the Qatargate where several elected official have been charged for receiving Qatari money against service (https://en.wikipedia.org/wiki/Qatar_corruption_scandal_at_the_European_Parliament ) isn't more discussed by media.

So I am curious, at the European level, which "party" (e.g. PPE, S&D) has done the most to prevent such a case to happen again ?