Britain must prepare for war with Russia within five years by building bunkers and investing in air defences, the former Army head has warned.

Gen Sir Patrick Sanders, who stood down as Chief of the General Staff last summer, said the UK needed to accept that war with Putin by 2030 was a “realistic possibility”.

In his most stark comments yet on the threat Britain faces from Moscow, Sir Patrick said he did not know how many more “signals” the British Government needed for it to realise that it must act to increase the nation’s resilience.

“If Russia stops fighting in Ukraine, you get to a position where within a matter of months they will have the capability to conduct a limited attack on a Nato member that we will be responsible for supporting, and that happens by 2030,” Gen Sir Patrick said in an interview with The Telegraph.

Gen Sir Patrick said as the former head of the British Army, there had been unsuccessful “conversations” with the Government about building bomb shelters for civilians and underground command centres for the military in preparation of an attack.

“It always came down to a conversation of it being too costly and not a high enough priority and the threat didn’t feel sufficiently imminent or serious to make it worth it,” he said.