The Digital Day coming amid big questions over the use of our personal data.
One German MEP said she was clear what she would be asking Zuckerberg right now.
"My question would be why Facebook did not inform the users as soon as they learned about the data had passed on," said Julia Reda.
"Because the problem, of course they can't control the fact that somebody else illegally use data for the wrong purpose. But apparently they have known this for a long time and they didn't inform users, they didn't inform the public and there I think is the real scandal."
Zuckerberg has not yet taken up a European Parliament offer to attend a session.
Next month, a strict new EU law comes in on data privacy, which the Facebook chief has said he agrees to "in spirit," but he's stopped short of committing to it as a standard for the social network globally.
"Here is a law that will protect personal data, a regulation in which the consent of users is at the heart of it," explained Mariya Gabriel, EU Commissioner for Digital Economy and Society.
"This means that each user has the right to know how their data is used and to freely decide to give their authorisation or not."
The EU law - known as the General Data Protection Regulation - is the biggest overhaual of online privacy since the birth of the internet.
One German MEP said she was clear what she would be asking Zuckerberg right now.
"My question would be why Facebook did not inform the users as soon as they learned about the data had passed on," said Julia Reda.
"Because the problem, of course they can't control the fact that somebody else illegally use data for the wrong purpose. But apparently they have known this for a long time and they didn't inform users, they didn't inform the public and there I think is the real scandal."
Zuckerberg has not yet taken up a European Parliament offer to attend a session.
Next month, a strict new EU law comes in on data privacy, which the Facebook chief has said he agrees to "in spirit," but he's stopped short of committing to it as a standard for the social network globally.
"Here is a law that will protect personal data, a regulation in which the consent of users is at the heart of it," explained Mariya Gabriel, EU Commissioner for Digital Economy and Society.
"This means that each user has the right to know how their data is used and to freely decide to give their authorisation or not."
The EU law - known as the General Data Protection Regulation - is the biggest overhaual of online privacy since the birth of the internet.
Read more: New EU digital law will 'protect personal data' | Euronews
