Boris Johnson led world efforts on Monday to “tighten the vice around Vladimir Putin’s regime”.
During a press conference, he slammed the Russian president for his “utterly repugnant” invasion of Ukraine.
The Prime Minister announced a further £175million in aid for the Ukraine, bringing the UK’s total commitment to nearly £400 million.
He said it is the moment for Ukraine’s friends “to create a coalition of humanitarian, economic and defensive military support” to ensure Mr Putin’s “catastrophic invasion” fails.
After hundreds, if not thousands, of civilians have been killed in Russian attacks in Ukraine, the Prime Minister accused Mr Putin of launching an “all-out onslaught on centres of habitation”.
As Parliament prepared to rush through a wave of legal moves to beef up sanctions against the Russian president and his allies, Mr Johnson said: “We are going to continue to work with colleagues to ensure that we tighten the vice around President Putin’s regime.
“What is happening now is that the President of Russia is doubling down.
“He has decided that he is going to continue with an all-out onslaught on centres of habitation in a way that we think is utterly repugnant. It’s clear that we are going to have to do more.”
Mr Johnson hailed the “heroic” Ukrainian resistance against the invasion.
Speaking with the Dutch Prime Minister Mark Rutte and Canadian leader Justin Trudeau, Mr Johnson said: “After 12 days, it’s already clear that Putin has made a miscalculation.
“He has underestimated the Ukrainians, their heroic resistance, he has underestimated their leader, and he has underestimated the unity of the West.
“We will continue as colleagues to do everything we can to strengthen that unity in the days ahead to ensure that Putin fails in this catastrophic invasion of Ukraine.”
Mr Trudeau said Canada is imposing new sanctions on 10 individuals in relation to the invasion of Ukraine.
Speaking following talks at Downing Street, he said: “This includes former and current senior government officials, oligarchs and supporters of the Russian leadership.
“The names of these individuals come from a list compiled by jailed opposition leader Alexei Navalny.”
The Dutch leader said his country was prepared to consider “all possible sanctions” but they must not generate “unmanageable risks” to energy supply in Europe.
Mr Trudeau added: “The focus is on the people of Ukraine and our solidarity with Ukraine pushing back against illegal Russian invasion of Ukraine and standing up for democracies around the world.”
It was announced Ukrainian President Volodymyr Zelensky will give a “historic address” to MPs on Tuesday by video link.
Commons Speaker Sir Lindsay Hoyle said he had granted the request for Mr Zelensky to read a statement to the House of Commons at 5pm on the Russian invasion of his country.
Sir Lindsay said: “Every parliamentarian wants to hear directly from the president, who will be speaking to us live from Ukraine, so this is an important opportunity for the House.
“Thanks again to our incredible staff for working at pace to make this historic address possible.”
On day 12 of the invasion, heartbreaking footage and pictures continued to surface from Ukraine.
It came after two days of failed ceasefires to let civilians escape the besieged city of Mariupol.
Unable to evacuate, hundreds of thousands of people have been trapped without food and water under relentless bombardment.
Ukrainian defence officials claim their forces have re-taken the eastern city of Chuhuiv, and an unconfirmed report said 30 Russian aircraft had been destroyed at the Kherson airfield.
Hundreds, if not thousands, of civilians have been killed in increasingly indiscriminate Russian artillery and air strikes. More than 1.5 million Ukrainians have fled abroad.
Russia denies deliberately targeting civilians but reports from the frontline appear to undermine this claim.
There have been more than 1,200 civilian casualties since the invasion, the Office of the UN High Commissioner for Human Rights said.
The World Health Organisation said there have been at least 16 attacks on healthcare facilities and staff after Russia invaded Ukraine.
“Attacks on health care violate international law & endanger lives,” WHO’s official Twitter said in a statement.
In the wake of the invasion, a string of major companies have now announced a boycott of Russia.
