The information is requested by the national GDPR enforcer so it bypasses the prevention written in the GDPR about news leaks.
Now there's a trial going around with this which blocked any further spread of that information until it's solved. It can be easily seen how the GDPR can be weaponized.
So the pretext they're using is that they want to see the information to make sure that the news organisation is not selling it or mishandling it to other third parties. In the process, they'll be able to get the information and maybe it will go to the people involved in the corruption charges (which is the head of one part of the Parliament).
For example, can't you check for all data to verify that the business is not doing anything with forbidden individuals or countries? (think OFAC)
I don't think GDPR allows anything more than any other law.