The Irish data watchdog is the lead regulator in the EU over Facebook, whose European subsidiary is based in Ireland, and has the option of fining the social network up to $1.63m.

Facebook revealed last week that hackers had attacked its site and stolen login codes meaning they could access almost 50m accounts. The DPC said less than 10% of those accounts were in the EU.

In a statement the DPC said the investigation would “examine Facebook’s compliance with its obligations under GDPR to implement appropriate technical and organisational measure to ensure the security and safeguarding of the personal data it processes.”