Observers have compared the crisis in Ukraine with Hitler's takeovers of Czechoslovakia and Poland. They have pointed to the similar use of disguised special forces to stir up tensions in disputed areas.
Charles, who is scheduled to meet Mr Putin at the D-Day commemorations in France on June 6, made his well-intentioned but unguarded comment during a visit to the Canadian
Museum of Immigration in Halifax, Nova Scotia.
The prince is on a whistlestop tour of Canada with the Duchess of Cornwall. They have 41 engagements in just three and a half days.
On Monday, local time, the pair paid a heartfelt tribute to Second World War veterans and their families over tea at the museum in Halifax's docks.
Prince Charles was introduced to Marienne Ferguson, a museum volunteer who fled to Canada with her Jewish family when she was just 13.
The 78-year-old was born in what is now the Polish city of Gdansk, a key flashpoint in the Second World War.
A free city under the terms of the Versailles Treaty after the end of the Great War, it was seized by the Nazis on the first day of fighting in 1939.
Mrs Ferguson and her parents, two sisters and grandmother had managed to obtain permits to sail to Canada. But other members of her family failed to flee before the German army arrived.
Along with an estimated six hundred Jews from the city, they were sent to Nazi camps where they met their deaths.
Mrs Ferguson was given the chance to tell her incredible story to Charles as she showed him the museum's exhibits.
At the end of the visit, and surrounded by media, Charles made his off-the-cuff comment about the situation in Ukraine. It was heard by several witnesses.
Mother-of-three Mrs Ferguson said: "I had finished showing him the exhibit and talked with him about my own family background and how I came to Canada.
"The prince then said 'And now Putin is doing just about the same as Hitler'.
"I must say that I agree with him and am sure a lot of people do. I was very surprised that he made the comment as I know they [members of the Royal Family] aren't meant to say these things but it was very heartfelt and honest.
"I told the prince that while my family and I were lucky to get a permit to travel, many of my other relatives had permits but were unable to get out before war broke out on September 1. They were sent to the concentration camps and died."
Former US secretary of state Hillary Clinton sparked uproar in Washington recently when she said very much the same as the heir to the throne.
Lashing out at Moscow's plan to issue passports to ethnic Russians in Crimea, she said: "Now, if this sounds familiar, it's what Hitler did back in the 1930s."
What is unusual, however, is for a senior royal to express an opinion publicly on such a clearly sensitive diplomatic issue.
Charles is often criticised for meddling in domestic affairs of state as well as the infamous 'black spider' memos - so called because of his scrawling handwriting - that he is said to frequently write to ministers on issues close to his heart. But international issues, particularly one as sensitive as this, are considered taboo.
A spokesman for Clarence House said last night they would not comment on a private conversation.
- Daily Mail
