It may be early days for Facebook's plan to integrate Messenger, WhatsApp, and Instagram, but one regulator already wants answers.

The Irish Data Protection Commission (DPC) has asked Facebook for an "urgent briefing" on the tech giant's proposal, which will see the three apps continue separately — but have their backend infrastructure unified.

"The Irish DPC will be very closely scrutinising Facebook’s plans as they develop, particularly insofar as they involve the sharing and merging of personal data between different Facebook companies," the statement reads.

"Previous proposals to share data between Facebook companies have given rise to significant data protection concerns and the Irish DPC will be seeking early assurances that all such concerns will be fully taken into account by Facebook in further developing this proposal."

"It must be emphasised that ultimately the proposed integration can only occur in the EU if it is capable of meeting all of the requirements of the GDPR."

Unifying the backend of these three apps means it could be easier for people to send messages across the platforms, for instance, simultaneously benefiting Facebook in ensuring users stick to the company's products.

It raises regulation and privacy issues, however, and marks a significant shift from the independence which was granted to the platforms from Facebook — Instagram's Kevin Systrom and WhatsApp's Jan Koum emphasized this when their apps were acquired by Facebook at the time.

In an interview with Forbes, WhatsApp co-founder Brian Acton said he was "coached to explain" to the EU's antitrust regulators that it would be "really difficult" to merge or blend data between WhatsApp and Facebook, shortly before the tech giant's acquisition in 2014.

Acton said neither he or Koum wanted to merge the systems, but Acton claimed he later found out that Facebook had already begun work on trying to blend data.

WhatsApp's plans to share personal data with Facebook were quashed last year, following an investigation from the UK's Information Commissioner's Office, after declaring such data transfer would be illegal.

Facebook's plan has also come under fire from Silicon Valley congressman Ro Khanna.

"This is why there should have been far more scrutiny during Facebook’s acquisitions of Instagram and WhatsApp which now clearly seem like horizontal mergers that should have triggered antitrust scrutiny," he tweeted on Sunday.

"Imagine how different the world would be if Facebook had to compete with Instagram and WhatsApp. That would have encouraged real competition that would have promoted privacy and benefited consumers."