AN MP has expressed his frustration after a cyber attack on Parliament prevented him from getting on with his duties.

Crawley MP Henry Smith tweeted yesterday: "Sorry no parliamentary email access today - we're under cyber attack from Kim Jong Un, (Vladimir) Putin or a kid in his mom's basement or something..." before adding he was off to the pub.

The "sustained" hack began on on Friday morning, according to reports in The Sunday Times, but MPs were only informed at 10.30pm on Friday night.

More than 10,000 Westminster staff have been told to change passwords after the "determined attack" on all user accounts looking for weak passwords.

Government sources say it appeared the attack has been contained.

MPs and peers have been warned they could face blackmail threats if hackers were successful in accessing sensitive material with one Whitehall official saying it was inevitable some information would have been stolen.

The Parliamentary computer system remained down this morning with Mr Smith urging constituents with urgent problems to email his Conservative email address instead.