The Liberal Democrats are demanding lessons are learnt on the first anniversary of a costly cyber attack on Gloucester City Council.
The hack has already cost the council £787,000 and there are fears the final bill could top £1 million.
Benefit payments, planning applications and house sales were all delayed after hackers compromised the council's IT systems in December last year.
The authority has had to rebuild all of its servers after the malware was able to access the council's computer software and cause havoc.
Most of the IT services have been restored and the council is making use of the cloud network, but the planning portal is still not fully operational.
Councillor Jeremy Hilton, leader of Gloucester Liberal Democrats, said last year's cyber attack was the second in a decade and there must not be a third.
"There cannot be a third cyber attack. To have one is bad luck but two or three and it starts to look sloppy and careless under the Tory misrule of the council," Councillor Hilton said.
"Moving a number of servers to the cloud should better protect the authority from further attacks but the Conservatives must put robust procedures in place to ensure it can never happen again."
While the IT systems were shut down council staff had to return to providing services manually, which interrupted regular work and key projects.
Councillor Hilton said: "There must be review of how the staff coped whilst the IT systems were down. What lessons were learned?
"We should pass on that information to the Local Government Association and publish it on the council's website.
"Lessons must be learnt and it must not be repeated.
"The job of a councillor was also undermined. Useful information that the council held, which was a benefit to good decisions, couldn't be accessed.
"Opposition councillors also had to ask many public questions to breakdown the attempt by the Conservative Cabinet to keep it all under wraps.
"The promise to webcast our meetings has not happened, with the excuse that it couldn't be because of the cyber attack. That excuse must now end."
Councillor Declan Wilson, Lib Dem group leader and finance spokesman added: "We know the cyber attack has cost the council at least £787,000 but the final costs remain unknown.
"It could well end up costing the council over £1 million.
"The cabinet member for finance, Hannah Norman, still has not provided councillors with the final total and will not say if it will be more or less than £1 million. She must give a definitive answer.
"The city council's annual budget for all services is around £14 million so to get hit with such a huge bill for the cyber attack is deeply troubling."
The Liberal Democrats are demanding answers from Tory bosses over the costly cyber attack on Gloucester City Council that has seen the personal data of residents put at risk.
