The regulator announced on Tuesday it would be investigating the circumstances surrounding the hack.
Earlier this month, the consumer credit reporting agency said a file containing 15.2 million UK records dating from between 2011 and 2016 was attacked during a cyber attack on its US parent company.
Of these, Equifax has identified 693,665 UK consumers who may have had their data accessed, including phone numbers, email addresses and partial credit card details. The agency is writing to these customers by post.
The data breach took place in May and compromised the information of 145.5 million US customers.
A spokesperson for Equifax said it is already working closely with the FCA and other authorities and that it welcomes “this opportunity to learn the lessons from this criminal cyber-attack in order for all businesses to better protect consumers in the future.”
Nicky Morgan MP, chair of the Treasury Committee, that the FCA was right to investigate and that the Committee would examine the case further when it takes evidence from the FCA later this month.