The Australian Signals Directorate,the government's key agency on cyber-security,moved swiftly in recent days to lock down and protect the network. Mr MacGibbon refused to say how long the hackers might have been in the network before they were detected.

All MPs,including ministers,use the parliamentary network. House Speaker Tony Smith and Senate President Scott Ryan said in a joint statement there was"no evidence that any data has been accessed or taken at this time,however this will remain subject to ongoing investigation".

They said they had no evidence the hack was an effort to"influence the outcome of parliamentary processes or to disrupt or influence electoral or political processes".

Mr MacGibbon declined to comment on whether the attack might be part of a Russian-style foreign interference campaign,pointing to Mr Smith and Senator Ryan's statement.

China has been responsible for several previous high-profile hacks on Australian government systems,including breaching Parliament’s computer network in 2011,which may have allowed Chinese spies to read the emails of MPs and their staff for months.

Fergus Hanson,a cyber expert with the Australian Strategic Policy Institute,said any data such as emails that were stolen could be used in various ways to wreak havoc with Australian democracy.

“It could be used to target one particular party … or used to discredit public institutions,to show that the Parliament may not be functioning the way we think it should be,and to undermine public trust,” he said.

“This is a great system to be targetting if you are a nation-state. Lots of juicy correspondence between staffers about who is doing what and dirt files on politicians.”

Mr Smith and Senator Ryan said that out of an"abundance of caution",user passwords had been reset.