In London, Boris Johnson was beginning a week of intense diplomatic efforts with foreign leaders to build a united front against Vladimir Putin, welcoming Canadian Prime Minister Justin Trudeau and Dutch Prime Minister Mark Rutte to Downing Street.

Russian forces continued their bombardment of Ukrainian towns despite the announcement of limited local ceasefires.

Previous attempts to create humanitarian corridors ended with shelling of civilians as they tried to flee to safety.

A Russian task force said a ceasefire would begin on Monday morning, the 12th day of the war, for civilians in the capital Kiev, the second city of Kharkiv, the southern port of Mariupol and Sumy.

But evacuation routes published by the Russian news agency RIA Novosti showed that civilians will only be able to leave to Russia and Belarus.

Mr Cleverly told the BBC: “It sounds cynical beyond belief. There is an opinion that Vladimir Putin believed there was a general desire among Ukrainians to be closer to Russia, to to be more Russian. I think that turned out to be complete nonsense in the circumstances that we see.

“Providing escape routes into the arms of the country that is currently destroying yours is nonsense.”

He added that “at the end of the day, the most humanitarian thing the Russians can do is to stop this totally illegal and totally unjustified invasion of Ukraine.”

Meanwhile, ministers were trying to move “faster and faster” with sanctions against the Kremlin.

The prime minister is expected to exert more pressure on international leaders to take further steps to remove Russia from the Swift payment system, while pushing them to back his six-point plan to tackle Russian aggression.

Meanwhile, Foreign Secretary Liz Truss said amendments to the Economic Crimes Bill – which is expected to be fast-tracked through the House of Commons on Monday – “would give us the ability to impose sanctions even more paralyzing against Putin and his regime”.

Labor said the legislation still gives Russian oligarchs a ‘free out of London’ card even though the grace period under measures to tackle so-called ‘dirty money’ has been cut by 18 months to six months, with the opposition calling for a further reduction to just 28 days.

Mr Cleverly told Sky News the government was working on a cross-party basis to push through the legislation.

“The ultimate goal is to make sure that the sanctions that we have already put in place, which are incredibly effective and have had a real impact on the Russian oligarchs, and in fact on the Russian economy, are further strengthened, and we welcome support from all parties in this regard.

Responding to criticism over the number of individual oligarchs targeted by sanctions, Mr Cleverly said: ‘We’ve had a very large number, over 200 individuals and entities, over £250 billion of Russian economic activity reduced, more than three million Russian companies are no longer able to finance themselves on the London market.

“So the fact that Vladimir Putin pointed the finger at us for criticism is a badge of honor.”

Shadow Business Secretary Jonathan Reynolds told BBC Radio 4’s Today programme: ‘I want to know where the treasure is buried. These are not just oligarchs, but also money launderers. It’s about tax evaders, I want to know where that money is.

“I think the reasonableness of that period is what will give us the chance to do that.”

The government has also been urged to do more to allow Ukrainians fleeing war to enter the UK.

The Interior Ministry revealed on Sunday that only “about 50” visas had been granted under Ukraine’s family program as of 10 a.m. Sunday.

Shadow Home Secretary Yvette Cooper tweeted: “Too slow. Too many hurdles for desperate families to jump through. The Interior Ministry completely fails to understand the urgency of the crisis.

But Home Secretary Priti Patel said the UK was “doing everything possible” to speed up efforts to grant visas to Ukrainians fleeing the conflict, and told The Sun she was looking at a ” humanitarian pathway” to allow all Ukrainian refugees who want to come to the UK to do so.

Mr Cleverly said the number of Ukrainians on visas to the UK would increase “very, very rapidly”, but the scale of the crisis was unprecedented.

“This is the biggest flow of refugees we have seen since World War II,” he told LBC.

The Home Office “had to create a system pretty much from scratch”, he said, and the process “will become faster and smoother and faster”.