Cyber attacks are attempts to damage disrupt or gain unauthorised access to computer systems, networks or devices (Picture: MOD).
A new report is warning ministers are not preparing properly for the growing threat of cyber-attacks on vital infrastructure.
The Joint Committee on National Security Strategy criticises a "wholly inadequate" response so far.
The parliamentary committee of senior MPs and peers says ministers are failing to act with "a meaningful sense of purpose or urgency" in the face of the cyber threat.
It said states like Russia are expanding their capability to mount disruptive cyber attacks but ministers are not doing enough.
The committee urged Theresa May to appoint a cyber security minister in the Cabinet Office to take charge of the efforts to build national resilience.
It said ministers had acknowledged the need to improve resilience but it said their efforts had failed to match the level of risk. The committee stated:
"While we applaud the aspiration, it appears the Government is not delivering on it with a meaningful sense of purpose or urgency."
The report went on to say: "We are concerned that the current complex arrangements for ministerial responsibility mean that day-to-day oversight of cross-government efforts is, in reality, led by officials, with ministers only occasionally 'checking in'."
"This is wholly inadequate to the scale of the task facing the Government, and inappropriate in view of the Government's own assessment that major cyber attacks are a top-tier national security threat."
The committee said ministers needed to do more to ensure the cyber threat was addressed at board level with an understanding that it must be "proactively managed".
The committee chair, former foreign secretary Margaret Beckett, said: "The Government should be open about our vulnerability and rally support for measures which match the gravity of the threat to our critical national infrastructure."
A Government spokeswoman said: "Ensuring our critical national infrastructure is secure and resilient against cyber attacks is a priority for the Government, which is why we are investing £1.9bn to improve our cyber capabilities."