Disruption to energy supplies after Russia’s invasion of Ukraine, and another pandemic, are two of the most significant risks to the UK shown in an updated government register that declassifies some threats for the first time.

In its first update for three years, the risk register rates the possibility of a “catastrophic” pandemic as 5% to 25% likely in a five-year period, upgrading its risk from the previous assessment of 1 to 5% likely.

It also ranks an attack on the UK’s infrastructure, such as its energy network, with a “significant” impact as 5% to 25% likely within a two-year period, disclosing this as a major risk for the first time. This category includes Russia deliberately disrupting energy supplies in Europe, or terror attacks on utility networks, nuclear facilities or fuel supplies.

“While the UK relies less on Russian energy than many other European countries, it is still exposed to disruption in European energy markets,” the document says. In the worst scenario, all transit gas that flows from Russia to European states is cut off for several weeks during winter, potentially leading to demand curtailment across Europe.

“A severe gas shortage in mainland Europe for a significant period could also negatively impact continental European gas-fired electricity generation capacity, which could affect the UK’s security of energy supply in winter, impacting household electricity consumers,” the register says.

The updated document was launched by Oliver Dowden, the deputy prime minister, listing 89 threats to the UK.

The Cabinet Office, which Dowden heads, said the grading of three major risks previously kept secret had now been made public: disruption of energy supplies, malicious drone attacks and damage to subsea cables carrying internet and communications data.

The new disclosures come after a House of Lords committee criticised the secrecy around the risk register. Some national security risks are still omitted from the document.

The most significant risk appeared to be another pandemic, with a reasonable worst case scenario of 840,000 deaths and 2.5% mortality rate, outstripping the number of Covid fatalities in the UK. The document also assessed the risk of a pathogen escape from a laboratory in the UK and found this to be very low, as well as probably not having a great impact.

Along with another pandemic, there are four other risks that are graded as possibly “catastrophic”. The failure of the electricity network and a large-scale chemical, biological, nuclear or radiological attack are both assessed as 1% to 5% likely within two to five years, while a civil nuclear accident or overseas radiation escape are rated as 0.2% to 1% likely.

The most likely major risks, at greater than 25% chance in the next two to five years and a “moderate” impact, were terrorist attacks in public places, tech failure in the financial services industry, an attack on a non-Nato ally, and disaster response in an overseas territory.

The threat of a malicious drone attack was rated “moderate” in impact, but only 0.2% to 1% likely in the next two years.

Both artificial intelligence and climate change are rated as “chronic” risks along with antimicrobial resistance, and serious and organised crime.

Dowden said the risk assessment was the most comprehensive ever published and highlighted that one of the UK’s “rising risks” was energy security. Visiting the Dogger Bank windfarm in the North Sea off the north-east coast, he said wind was a low cost and clean energy that “enables us to stand up to Putin’s energy ransom”.

Matt Collins, the deputy national security adviser, said the updated register “based on the government’s internal, classified risk assessment, offers even more detail on the potential scenarios, response and recovery options relating to the risks facing the UK, ranging from terrorism to conflicts and natural disasters”.

The register takes account of recent events in profiling risks, and cites the murder of the Conservative MP Sir David Amess in its assessment of the assassination of a public figure, for which it says there is a likelihood of more than 25%. Prior to that, the Labour MP Jo Cox was also murdered.

Post Source Guardian