Britain and allies "took their eye off the ball" over Russia in the aftermath of the Cold War, the Foreign Secretary has admitted.
The West "essentially provided the funding" for Moscow to boost its military by buying Kremlin oil and gas - at the same time as slashing spending on their own Armed Forces, Liz Truss told the Commons Foreign Affairs Committee.
Countries need to wean themselves off Russia’s hydrocarbons and “all the free world need to rethink their economic dependence” on Vladimir Putin 's regime, she told MPs.
Ms Truss said: "I think post-Cold War the West took its eye off the ball.
"Defence budgets were cut, there was too much entering into trade and economic relationships without understanding the underlying strategic dependency that would lead to."
But cash pumped into the Russian economy helped finance an overhaul of its forces, she admitted.
The invasion of Ukraine "shattered the security architecture of Europe" - and more funding needs to be poured into NATO, Ms Truss told MPs.
She said: "There's no doubt that the West didn't act early enough or decisively enough.
"The reality is President Putin did not take the threats of deterrence seriously enough."
She added: "What we have to do now is we have to strengthen Nato, we particularly have to strengthen the eastern flank.
"We have already deployed more troops into Estonia but there is more to do.
"We have to be serious about defence spending, right across Nato."
Ms Truss also confirmed that the Britain's ambassador to Ukraine has left the country because of the "serious security situation".
It was previously announced that the ambassador, Melinda Simmonds, had moved from the capital Kyiv to Lviv in western Ukraine, where the threat was considered less acute.
Boris Johnson warned that there could be no return to the status quo after Russia's brutal invasion of Ukraine - and branded Vladimir Putin's tactics "repugnant".
Speaking at a Downing Street press conference alongside Canadian PM Justin Trudeau and Dutch premier Mark Rutte, he said the three countries "stand shoulder to shoulder against Russia's barbaric invasion of Ukraine".
The PM continued: "I do think that the world is clearly changing and I think that what we can't do post the invasion of Ukraine is assume we can go back to a status quo... a kind of new normalisation in the way that we did after the invasion of Crimea in 2014, or the seizure of Crimea and the Donbas area.
"We've got to recognise that things have changed and that we need a new focus on our collective security. And I think that is increasingly understood by everybody."
It comes after Mr Johnson claimed the West had “turned the other cheek” to Russia “for too long” in a lengthy essay for the New York Times.
Warning “we need to prepare now for even darker days ahead”, he added: “No-one can say we were not warned: we saw what Russia did in Georgia in 2008, Ukraine in 2014 and even on the streets of the British city of Salisbury.”
The PM has issued warnings about this before - but he failed to mention that he was previously branded a “Putin apologist” during the Brexit campaign, when he sought to blame the EU over Russia’s 2014 annexation of Crimea.
The Tories have been urged to return £2m of donations from people or firms with links to Russia but the PM has refused to apologise or act on it.
He has argued that not all Russian dual nationals should be excluded based on the actions of Putin and his cronies.
The calls for greater defence spending come after sweeping cuts to the UK armed forces in recent years.
As of 1 October 2021, the “trained strength” of the British Army is 77,526 personnel, 29,688 in the Royal Navy and Royal Marines, and 29,913 in the Royal Air Force.
That gives a total of 137,127 in the UK Armed Forces.
But this will be cut by around 2,000 to achieve a smaller Army as envisaged in ‘Defence in a Competitive Age’ command paper.
The target is to cut the Army, which has already been slashed back, by nearly 5,000 to 73,000.
The Navy and RAF would increase in size slightly, to 30,450 and 31,750 respectively.
