Fewer than 90 email accounts were compromised in this weekend's cyber attack on email accounts in Westminster, the PA has reported.
Some 10,000 MPs and their aides were locked out of their accounts over the weekend after it emerged they had come under a "sustained and determined" attack.
Reports suggested the hack was state-sponsored, with fingers pointed at Russia.
Today a parliamentary spokesperson said: "Parliament's first priority has been to protect the parliamentary network and systems from the sustained and determined cyber attack to ensure that the business of the Houses can continue. This has been achieved and both Houses will meet as planned tomorrow.
"Investigations are ongoing, but it has become clear that significantly fewer than one per cent of the 9,000 accounts on the parliamentary network have been compromised as a result of the use of weak passwords that did not conform to guidance issued by the Parliamentary Digital Service. 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.
"Parliament is now putting in place plans to resume its wider IT services"
This morning the Sunday Times quoted a senior Whitehall official saying it was "inevitable" some information had been stolen.
The news came after dozens of NHS hospitals were crippled by a massive ransomware attack last month.