The Prime Minister has told Conservative MPs the war between Russia and Ukraine is a "moment of choice" between "freedom and oppression".
Speaking at the Conservative party spring conference in Blackpool, Boris Johnson added that the conflict is a "turning point for the world".
"I know there are some around the world, even in some western governments… who say that we're better off making accommodations with tyranny," he said.
"I believe they are profoundly wrong and to try to renormalise relations with Putin after this, as we did in 2014, would be to make exactly the same mistake."
The Prime Minister added that for Russian president Vladimir Putin, a free and democratic Ukraine was a threat to his style of rule.
"With every year that Ukraine progressed – not always easily – towards freedom and democracy and open markets, he feared the Ukrainian example and he feared the implicit reproach to himself," he said.
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"Because in Putin's Russia you get jailed for 15 years just for calling an invasion an invasion, and if you stand against Putin in an election you get poisoned or shot.
And Boris Johnson said it was a "tragedy" the lack of democracy in Russia meant Putin was not challenged as he launched his "disastrous" invasion.
"I don't believe that democratic freedoms are going to sprout any time soon in the Kremlin, far from it," Mr Johnson said.
"But with every day that passes I think that Putin becomes a more glaring advertisement for the system that he hates and despises, and it becomes ever more obvious why we have to stick up for Ukraine."
The Prime Minister also thanked Defence Secretary Ben Wallace for urging him to "read Putin's crazy essay" several months ago ahead of the invasion and said the pair, along with Foreign Secretary Liz Truss, speak daily about the situation in Ukraine.
Also speaking at the conference, Ms Truss said: "We have seen the most horrific, horrible scenes in Ukraine.
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"We have seen a war in Europe for the first time in decades and we are seeing incredible bravery from the Ukrainians and deeds of valour that will be written about for generations to come.
"Britain has stepped up, now we must do even more.
"(Vladimir) Putin must lose in Ukraine, and with Britain at the forefront we will ensure he does."
Mr Wallace said Vladimir Putin's "arrogant assumptions have directly led to the casualties and attrition among the Russian army".
"The Kremlin assumed that Ukraine would not fight – he was wrong.
"The Kremlin assumed his army was invincible – they were wrong.
"And they assumed the international community would splinter and they've been proven wrong," he added.