The warning comes as the National Cyber-Security Centre (NCSC) reported an increase in more serious cyber attacks this year.

Criminal hacks on Marks and Spencer, The Co-op and Jaguar Land Rover have led to empty shelves and production lines being halted this year as the companies struggled without their computer systems.

Organisations need to "have a plan for how they would continue to operate without their IT, (and rebuild that IT at pace), were an attack to get through," said Richard Horne, chief executive of the NSCS.

Firms are being urged to look beyond cyber-security controls toward a strategy known as "resilience engineering", which focuses on building systems that can anticipate, absorb, recover, and adapt, in the event of an attack.

Preferably the plans should be in paper form or stored offline, the agency suggests.

Although the total number of hacks that the NCSC dealt with in the first nine months of this year was, at 429, roughly the same as for a similar period last year, there was an increase in hacks with a bigger impact.

The number of "nationally significant" incidents represented nearly half, or 204, of all incidents. Last year only 89 were in that category.

A nationally significant incident covers cyber-attacks in the three highest categories in the NCSC and UK law enforcement categorisation model:

Amongst this year's incidents, 4% (18) were in the second highest category "highly significant".

This marks a 50% increase in such incidents, an increase for the third consecutive year.

The NCSC would not give details on which attacks, either public or undisclosed, fall into which category.

But, as a benchmark, it is understood that the wave of attacks on UK retailers in the spring, which affected Marks and Spencer, The Co-op and Harrods, would be classed as a significant incidents.

One of the most serious attacks last year, on a blood testing provider, caused major problems for London hospitals. It resulted in significant clinical disruption and directly contributed to at least one patient death.

The NCSC would not say which category this incident would fall into.

The vast majority of attacks are financially motivated with criminal gangs using ransomware or data extortion to blackmail a victim into sending Bitcoins in ransom.

Whilst most cyber-crime gangs are headquartered in Russian or former Soviet countries, there has been a resurgence in teenage hacking gangs thought to be based in English-speaking countries.

So far this year seven teenagers have been arrested in the UK as part of investigations into major cyber-attacks.

As well as the advice over heightened preparations and collaboration, the government is asking organisations to make better use of the free tools and services offered by the NCSC, for example free cyber-insurance for small businesses that have completed the popular Cyber-Essentials programme.

Have plans on paper in case of cyber-attack, firms told