BRADFORD district MPs spoke of their concerns after being told they could only access email from Parliament after hackers hit the Westminster network with a "sustained and determined" bid to break into the email accounts of MPs, peers and their staff.

Users of the Westminster system have been unable to access their accounts remotely due to defensive measures put in place by parliamentary authorities to deal with the hack, thought to have begun on Friday.

Bradford South Labour MP Judith Cummins said today: “The cyber attack on Parliament in recent days was deeply concerning. This incident starkly demonstrates that the threats we face are ever changing, and we must remain vigilant as a country and indeed as a democracy.

“An internal investigation into this attack, with the support of the National Cyber Security Centre, is now underway. As this investigation unfolds I will be pressing authorities to make sure our systems are able to withstand these increasingly common attacks.”

Shipley Conservative MP Philip Davies added: "We've been told we can only access our emails from Parliament.

"It means my constituents will be messaging me and I am not able to answer them.

"I pride myself on replying to email messages promptly but my fear is that messages I am getting are being banished to the junk basket and may be lost for ever.

"I am going down to London this afternoon as normal and will be attempting to answer the emails I have received and that I cannot currently answer, from there. We just have to wait until it is sorted."

The issue has raised blackmail fears. The National Cyber Security Centre (NCSC) and National Crime Agency are probing the incident, which comes after reports that passwords for Cabinet ministers and MPs were being sold online by hackers.

Tory MP Andrew Bridgen said such an attack "absolutely" could leave some people open to blackmail.

He said: "Constituents want to know the information they send to us is completely secure."

An email sent by parliamentary authorities to those impacted by the attack said that after "unusual activity" was spotted, "closer investigation by our team confirmed that hackers were carrying out a sustained and determined attack on all parliamentary user accounts in an attempt to identify weak passwords".

A parliamentary spokesman said: "We have discovered unauthorised attempts to access accounts of Parliamentary networks users and are investigating this ongoing incident, working closely with the National Cyber Security Centre.

"Parliament has robust measures in place to protect all of our accounts and systems, and we are taking the necessary steps to protect and secure our network.

"As a precaution we have temporarily restricted remote access to the network. As a result, some Members of Parliament and staff cannot access their email accounts outside of Westminster.

"IT services on the parliamentary estate are working normally. We will continue to keep members of both Houses of Parliament and the public updated as the situation develops."

International Trade Secretary Liam Fox said the incident was no surprise after the recent major hacking attack against the NHS.

Dr Fox added: "We know that there are regular attacks by hackers attempting to get passwords.

"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, including having complex and therefore safer code words."