The Russian Foreign Ministry has issued a furious condemnation of Prince Charles for his comparison of President Puting to Adolf Hitler, calling the comments "outrageous and low".
A spokesman said: "If these words were truly spoken, then without doubt, they do not reflect well on the future British monarch.
"We view the use of the Western press by members of the British royal family to spread the propaganda campaign against Russia on a pressing issue - that is, the situation in Ukraine - as unacceptable, outrageous and low."
Putin aides have demanded an explanation from the Foreign Office amid the furore over Prince Charles’s likening of Vladimir Putin to Adolf Hitler.
Prince Charles is due to attend the same World War Two memorial as President Putin on June 7.
Moscow’s minister counsellor in London, Alexander Kramarenkohas has insisted on face-to-face talks, reports say.
"The Russians have said they want to discuss this issue. We will have to see how they decide to play it," a Whitehall source told the Daily Mail.
A senior Russian diplomatic source was quoted by the Daily Telegraph saying: "It's not clear if it is an official position. The response from Clarence House is it was a private talk. We hope there is nothing behind it. But it is unclear to us: what does it mean? He is the future king, after all."
The source told the newspaper the comments were particularly sensitive given the scale of Russian casualties in the fight against Hitler's regime in the Second World War. "It is very serious. Every family in our country lost someone in that war.".
Denis Pushilin, an ethnic Russian separatist leader in Donetsk, eastern Ukraine, said the remark offended ordinary Russians. "Putin represents the country which defeated fascism," he said. "The comparison with Hitler is totally absurd, groundless and unfair."
Charles has also been lambasted in the Russian media, with business-ru.com calling him the "elderly Prince of Wales, the oldest heir in the history of Great Britain, who failed to control himself and follow protocol."
"His uncle Edward VIII clearly sympathised with the Nazis," the piece said. Daily newspaper Moskovskij Komsomolets said the Prince of Wales could be "triggering an international scandal".
The Kremlin has remained tight-lipped. Putin's spokesman, Dmitry Peskov repeatedly refused to discuss the issue telling Sky News Moscow was "not commenting right now". One Kremlin source told the Sun they "couldn't trust" the Daily Mail's version.
Sergey Nalobin, the parliamentary counsellor at the Russian Embassy in London, tweeted his displeasure at the remarks. "Members of the royal family do not have the right to make such statements. Parliament is unlikely to be happy," he said.
With regards to the meeting at the memorial, Nalobin said: "As far as I know, a bilateral meeting was not planned. They just will participate in the same memorial ceremonies."
The Prince reportedly compared Putin to the Nazi dictator during a visit to an immigration museum in Halifax, Nova Scotia.
Jewish museum volunteer Marienne Ferguson, 78, told the Daily Mail that she had told Charles how she and her family fled the Nazis during the Second World War, and said that he responded: "Putin is doing just about the same as Hitler."
All three British party leaders have defended the Prince's right to his opinion. David Cameron told the BBC he was "not going to comment on the private conversations of anyone, least of all Prince Charles. Of course, everyone’s entitled to their private opinions."
Labour leader Ed Miliband said Charles "has got a point about President Putin’s actions and he is absolutely entitled to say that there are real concerns about that.
"Lots of people across the country will share Prince Charles’s concern about President Putin and his actions in the Ukraine."
Deputy Prime Minister Nick Clegg, said he did not think that the Royal Family "have to enter into some Trappist vow of silence."
On Tuesday, the Prince decided to take a poke at a different bear, this time a polar bear as part of a training session at the Assiniboine Park Zoo, feeding it a peanut sandwich.
Later, Charles appeared to have completely brushed off the controversy... by throwing paper planes towards the media.
He appeared in good spirits when he arrived at Stevenson Hangar in Winnipeg, Manitoba, with the Duchess of Cornwall and smiled as they were greeted by dozens of local students.
He was introduced to Canadian Prime Minister Stephen Harper and Charles and Camilla were given the chance to test the flight of their own paper planes by throwing them at a target, which was positioned next to number of photographers gathered to take their picture.
"Yes!", the Prince said as his first effort hit a cameraman.
"It wasn't such a great design," he added.
The Prince and Duchess will complete their four-day tour of Canada later at an official farewell ceremony at Manitoba's Legislative Building.