It is believed that the use of weak passwords as many as 90 parliamentary email accounts were effected by a cyber-attack on Friday.
A spokesperson said that the hacking impacted less than 1 per cent of the 9,000 accounts using the system.
As part of the response to the cyber-attack, remote access to emails was disabled as officials sought to protect from future attacks and limit the effects of this hack.
It is believed that the attack was enabled by a number of users having “weak passwords”, with an investigation set to take place to assess the damage in terms of data loss.
Parliament will continue with business as usual and there are plans to restore IT services to full use.
Multiple MPs confirmed that access to email accounts was restricted following the hacking, with no-one able to use their email accounts outside of Westminster.
A spokesman said: “As they are identified, the individuals whose accounts have been compromised have been contacted and investigations to determine whether any data has been lost are under way.”
International Trade Secretary Liam Fox said: “We have seen reports in the last few days of even cabinet ministers’
passwords being for sale online.
“We know that our public services are attacked so it is not at all surprising that there should be an attempt to hack into parliamentary emails.
“And it’s a warning to everybody, whether they are in Parliament or elsewhere, that they need to do everything possible to maintain their own cyber-security.”
The incident is currently being investigated by the National Crime Agency and the National Cyber Security Centre.