The whistleblower, Christopher Wylie, is testifying Wednesday before the Senate Judiciary Committee.
The committee had issued a letter containing 39 questions to Facebook, which were answered by the company's Chief technology Officer Mike Schroepfer in lieu of Zuckerberg.
Tajani said Zuckerberg had agreed to meet members of the European Parliament that lead its political groups, as well as lawmakers from its justice committee.
It has today published Facebook's answers, which were submitted to the committee yesterday - some three days after the deadline - and, somewhat unsurprisingly, the MPs said that these also fail to fully address their concerns.
Even though Facebook suspended the app on April 7, more than 6 million people have completed the tests on myPersonality and provided sensitive information about their private life.
You can delete your Facebook account say, angry users.
The individuals responsible for securing the data were University of Cambridge's Psychometrics Centre members Michal Kosinski and David Stillwell.
DCMS Committee chair Damian Collins expressed his dissatisfaction at Facebook's response.
For markets to perform well, customers should be given complete and understandable information on the nature of the services they are buying, even those that have a zero monetary price as in the case of Facebook.
However, it appears that the anonymisation was done in such a poor fashion that it might not be hard for a determined party to de-anonymise the data and piece together intimate details of individuals using the rich data set. The most grounded connect with the earlier data harvesting, however, is that the University of Cambridge's Psychometrics Center controlled the two informational indexes.