A former UK defence chief has warned “dire consequences” would follow if European leaders fail to hold their nerve and continue to support Ukraine.

Lord Stirrup, who served as head of the Armed Forces between 2006 and 2010, acknowledged there are “signs of growing war weariness” and a desire to end the conflict whatever it takes.

But he said this would be a “disastrous mistake” and make the prospect of a wider war more likely, as he predicted Russian president Vladimir Putin would ultimately ignore any settlement with Ukraine.

The appearance of North Korean soldiers in the conflict and the widening of the pool of prisoners, which Russia seeks to recruit soldiers from for the frontline underscores the difficulties that Putin is facing

Western officials earlier this month said they could not “see any prospect for a negotiation anytime soon” over the war, which has been ongoing since 2014 with Russia launching a full-scale invasion in February 2022.

Speaking during a House of Lords debate, Lord Stirrup said it has been a “difficult” year for Ukraine as weapons and personnel shortages are “hampering” its efforts to deal with the “grinding war of attrition” pursued by Russia.

He told peers: “But we should not assume that all the pressures are on the Ukrainian side. The appearance of North Korean soldiers in the conflict and the widening of the pool of prisoners, which Russia seeks to recruit soldiers from for the frontline underscores the difficulties that Putin is facing.

“The FCDO (Foreign, Commonwealth and Development Office) assesses that these difficulties will reach crisis proportions by the end of 2025/beginning of 2026. The question then is how Ukraine is to stay in the fight until then.

“But for Ukraine to stay in the fight, Europe and ideally the United States must stay in the fight. In both regions, however, there are signs of growing war weariness and a desire to end the conflict whatever it takes. This would be a disastrous mistake.”

On the “logical consequences” of such a near-term settlement, Lord Stirrup said he presumed an international agreement would be drawn up and signed by both sides.

But the independent crossbench peer warned: “We’ve been there before and we’ve seen only too clearly how little Putin regards or respects such agreements.

“The moment he feels they constrain his ambitions, he casts them aside without a second thought. Any piece of paper to which he puts his name would have about as much value as the one Neville Chamberlain waved in front of the cameras at Heston Aerodrome in 1938.”

European leaders need to do a much better job at explaining to their citizens the dire consequences that would attend a failure of nerve over Ukraine

Lord Stirrup said neither side would be satisfied with an outcome that left the other in control of part of Ukraine, explaining: “Putin would simply pursue his assault on his neighbour by undercover means while the Ukrainians would do the same in an effort to regain their lost territories until open fighting eventually broke out again.”

He went on to express concerns over potential nuclear proliferation and Russia using food as a “political tool” to spread its “malign influence more widely” in Africa.

Lord Stirrup concluded: “I don’t aim to convince the minister or the Government, I do not doubt their resolve.

“But European leaders need to do a much better job at explaining to their citizens the dire consequences that would attend a failure of nerve over Ukraine.

“Negotiating from a position of relative weakness would not bring an end to the conflict, it would carry huge nuclear risks, it would create fissures within Western Europe, it will weaken deterrence and it’d make a wider war more rather than less likely.

“It will leave our children and grandchildren a fearful legacy for which they would surely and rightly condemn us.”

Regardless of who wins the US election, it is pretty clear a new US president will be looking towards European Nato allies to step up and take greater responsibility for European security

Conservative former Foreign Office minister Lord Ahmad of Wimbledon acknowledged the “wise words and wisdom” from Lord Stirrup.

He said: “A bit of learning here for ministers: listening to the noble and gallant Lord was something I found extremely beneficial.”

Labour former minister Lord Spellar, making his maiden speech, said: “I also warn, as Lord Stirrup did, against the complacent view that a deal with Putin that allows him to claim victory will end the war.

“It may end the battle, it will not end the war and we need absolutely to understand that.”

Opening the debate, defence minister Lord Coaker reiterated the UK Government’s support for Ukraine as he said Russia’s war represented a “sustained attack” on the United Nations Charter and the rules and norms that underpin security and prosperity.

He said: “That is why Russia must lose and be seen to lose because global security is indivisible. What happens in Ukraine has an impact around the world.”

Lord Coaker also told peers: “Regardless of who wins the US election, it is pretty clear a new US president will be looking towards European Nato allies to step up and take greater responsibility for European security.”

Conservative peer Lord Balfe said he was “not part of the consensus” in the House, saying: “We need to stop this war and we need to start talking, preferably from our present position which is one of moderate strength.

“What we don’t want to be doing is talking in the aftermath of a downturn in American support when Putin thinks, quite rightly, that the whole game is over in his favour.”