Iran is being blamed for a cyber attack on parliament that compromised MPs' email accounts.
Blackmail fears were raised when hackers tried to break into the system used by MPs, peers and staff by searching for weak passwords.
Around 90 of the 9,000 email accounts were undermined in the "sustained and determined" attack in June.
Investigators say they have traced the source of the hit to the Tehran regime, according to The Times.
The House of Commons said it did not comment on security matters.
A National Cyber Security Centre spokesman said: "It would be inappropriate to comment further while enquiries are ongoing."
The reports come hours after the Microsoft president said that North Korea has carried out the WannaCry ransomware attack that took down much of the NHS systems earlier this year.
Brad Smith warned that cyberattacks by nation-states have become more frequent and more severe.
Meanwhile, Iran was also facing attacks by Donald Trump as the threatened to pull the plug on a nuclear deal after claiming that it was insufficient.