Prince Charles should abdicate and stand for election to parliament if he wants to make political statements, a Labour MP has said.
Mike Gapes, the former chairman of the Commons foreign affairs committee, said the heir to the throne should consider giving up becoming king after he was reported to have compared Vladimir Putin to Hitler.
"If Prince Charles wants to make controversial statements on national or international issues he should abdicate and stand for election," Gapes said on Twitter. "In constitutional monarchy policy and diplomacy should be conducted by parliament and government. Monarchy should be seen and not heard."
Gapes, the MP for Ilford South, did not defend the Russian president but said the normal "free speech" argument did not apply to Prince Charles. "If you are heir to throne or monarch what you say matters," he said.
"It is for parliament and government to use appropriate language to condemn illegal annexation of Crimea. Prince should stop freelance foreign policy."
Prince Charles' remark came during a tour of the Museum of Immigration in Halifax, Nova Scotia, where the Prince and the Duchess of Cornwall paid tribute to Second World War veterans and their families.
Jewish museum volunteer Marienne Ferguson told the Prince that she fled to Canada with her family shortly before the Nazis annexed the Baltic coastal Free City of Gdansk in 1939.
After meeting Charles, Mrs Ferguson, 78, told the Daily Mail: "The Prince 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."
The comments are not the first time the Prince has commented on political affairs. Letters he wrote to a number of government departments between 2004 and 2005 are the subject of a legal battle over whether their contents should be disclosed.
The Guardian has been trying to make the letters public under the Freedom of Information Act and in September 2012 the High Court ruled in its favour.
The newspaper said the battle was being fought to shed more light ''on the way the heir to the throne seeks to influence government ministers even though he holds no elected position''.
But Attorney General Dominic Grieve has attempted to block the release of the letters, claiming they undermine the principle of the heir to the throne being politically neutral.