A former Nato chief has warned Russian President Vladimir Putin that an attack on any member of the nuclear-armed alliance would pose “an existential risk to the Russian motherland”.
Lord George Robertson of Port Ellen said the collective defence guarantee, known as Article 5, “goes well beyond normal red lines”, in a hard-hitting speech at Westminster directed at the Kremlin.
The Labour peer, who was Nato secretary general from 1999 to 2004, is the only person to have announced the activation of the clause, after the 9/11 terrorist attacks in the US.
The former defence secretary told Parliament a Russian victory in Ukraine would be “the greatest nuclear threat” faced, and stressed the urgent need to stop this happening, including by providing more military assistance.
Lord Robertson was speaking in a debate on the resilience of the UK armed forces during cutbacks and the Russian invasion.
“What is increasingly clear is that Vladimir Putin has declared war on the West," he said.
“What is also clear is we are not responding adequately to that overt challenge to our countries and what we stand for. There is no visible urgency in our national behaviour.
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“Our UK defences need strengthening. That doesn’t just mean spending more on defence. It means replenishing the stocks that we are giving to the Ukrainians today.
“We need to give the Ukrainians more. If as ministers continually say the Ukrainians are fighting for themselves, their country and for us, as indeed they are, then holding stocks and equipment here, when our frontline is actually in eastern Ukraine, then we leave ourselves dangerously exposed."
Lord Robertson also appeared to dismiss calls by some for an “off ramp” for Moscow from the conflict, drawing parallels with the Russian retreat from Afghanistan in 1989.
“They were faced there with an endless unwinnable war costing lives and precious resources, so the Kremlin ordered the mighty Red Army of the Soviet Union to come home," he said.
“Nobody was asking at that time for an off ramp or for some ceasefire or some face-saver for the Russians.
"They simply folded their tents and left. And 32 months later there was no Soviet Union.”
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Lord Robertson issued a warning to Mr Putin: “We need to tell Vladimir Putin this. One step over the Article 5 Nato line and there will be an existential risk to the Russian motherland.
“And here’s another message for the man in the Kremlin, who gave us this terrible war, speaking as I do as the only person ever to announce the invoking of Article 5 – that guarantee that an attack on one Nato country should be seen as an attack on all of them.
“Can I tell Vladimir Putin — I met him nine times during my time in Nato and at that time we did good business together — but I tell him now the Article 5 guarantee of a nuclear weapons alliance goes well beyond normal red lines.”
Conservative defence minister Baroness Annabel Goldie said: “Our safety and that of our allies depends on Ukraine winning and Russia losing.
“Since the start of the conflict the United Kingdom has been a leading supporter of Ukraine. We have underlined that we are in this for the long haul.
“We work closely with the armed forces of Ukraine, we analyse with them what they think their needs are. We don’t do that in a silo on our own.
"We consult with our allies and our partners so that we are ensuring that our singular contributions achieve the best aggregate output in terms of impact and effect.”