Zuckerberg's absence from the hearing, having turned down several invitations to appear before the global committee, was noted by an empty chair with Allan answering questions in his stead. Lawmakers from Britain, Canada, France, Belgium, Brazil, Ireland, Latvia, Argentina and Singapore attended the hearing.
Facebook's outgoing head of public policy and communications, Elliot Schrage, assumed responsibility for hiring the Definers firm, while Zuckerberg said he was not aware of Facebook ties to the firm.
Mr Collins, who chairs the culture media and sport select committee, used powers to get hold of the documents from Ted Kramer, the founder of USA app developer Six4Three.
Lawmakers from the United Kingdom and other nations lambasted Facebook during the hearing for abusing public trust and failing to provide honest answers to questions about the misuse of user data.
Zuckerberg declined the invitation and instead sent a man named Richard Allen, a VP of policy solutions.
Alluding to the Six4Three emails, Labour MP Clive Efford said the committee had "seen evidence" regarding the closure of third-party apps on the network which "could not pay large sums of money for mobile advertising" and closing apps "so that Facebook can move into that area and make money".
The lawmakers - from the U.K., Canada, Brazil, Latvia, Argentina, Ireland, Singapore, France and Belgium - have repeatedly asked for Facebook CEO Mark Zuckerberg to appear before their "grand worldwide committee".
The documents were ruled sealed by a San Mateo, California Superior Court judge after months of legal wrangling between Facebook, Kramer's company Six4Three, and media organizations.
The seizure was invoked by MP Damian Collins, who also organized nine-nation 'Grand Committee on Disinformation'.
Ivanka Trump Defends Her Use of a Private Email Account
She says she didn't delete any of them. "So there's no connection between the two things". Numerous emails were in violation of public records rules, the paper reported .
Collins did, however, reveal that in October 2014, an engineer at Facebook discovered that Russian operatives used a Pinterest API key to pull over 3 billion data points per day from Facebook users.
This isn't the first time that Zuckerberg has refused to appear before British lawmakers.
The Facebook founder and CEO was asked to attend by the committee.
Allan said there have been a "number of actions taken" against developers but added, "I don't have in front of me today all of the answers to all of the questions".
Collins said the committee is still going through the papers and deciding which documents are in the public interest, but confirmed they would be published "within the next week or so". "To the extent this is all clarified and we have a clear playbook to work from, that would be very helpful", he said.
Lord Allan could not say whether the company knew about the alleged data access or whether relevant authorities were notified, but claimed the email cache was "at best partial, at worst potentially misleading".
Nathaniel Erskine-Smith, another member of the Canadian Parliament, pressed Allan over whether a user signing up for Facebook could reasonably be seen as "meaningful consent" - the standard under Canadian privacy law - for the company allowing others to access that data.
"You are the arbiter right now of the news cycle around the world because of your video metrics", Angus said.
At the hearing, Allan answered a question from a Canadian representative about whether Facebook would entertain antitrust regulation.